EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Electro Fan on May 25, 2015, 11:38:48 pm
-
Thanks to the ever stimulating EEV forum, I happened across a thread that was started by Bidski on LNAs which included this post by VK5RC:
https://www.eevblog.com/forum/beginners/100mhz-lna/msg679432/#msg679432 (https://www.eevblog.com/forum/beginners/100mhz-lna/msg679432/#msg679432)
In the post VK5RC mentioned that he has been building an EME (Earth Moon Earth) communications system. The concept is certainly understandable and believable technologically but the notion that the knowledge, skill, and wherewithal exists for an individual to build such a system seems very impressive, if not astonishing; apparently it is a doable challenge. My guess is that it's beyond my abilities but I thought it would be worth some research to learn what's involved. I figured maybe some others might find this interesting...
In doing some reading I found this excellent article:
http://www.k4lrg.org/Projects/K4MSG_EME/ (http://www.k4lrg.org/Projects/K4MSG_EME/)
Looks like it requires a transmitter, maybe 100 watts or less?
- Might need a license?
Needs a receiver that can pick out a signal about 24 dB below the noise floor?
- Kind of an exciting challenge by itself
But what really caught my attention is the graph showing the monthly distance (between Earth and Moon) and signal degradation. Checkout the big spike - what's that? Noise from the Sun? Nope.
"The smaller degradation peak occurs when the Moon is roughly coincident with the Sun, while the very large peak occurs when the Moon is passing in front of the Milky Way, a *HUGE* source of galactic noise!" Wow! (I suppose every astronomer knows this but I found it impressive to see the extent to which "Galactic Noise" is present, revealed, and quantified on the graph.)
Ok, that's all I know so far but if anyone wants to discuss how practical or difficult an EME project might be, please feel free to chime in. Perhaps VK5RC and others who have experience can provide some guidance. Don't know if K4MSG (author of the article linked above) visits the EEV forum but maybe he would be up for advising as well.
EF
-
EME is certainly a very interesting sector of ham radio and is well documented as well. You don't need to be an expert to to do it but it can be challenging to get it right.
You will definitely need a license. I always advise people to stick to the law and get a license, but for screwing around with a watt or two you really needn't bother. However EME is very difficult to do on low power so get a license first if you plan to do this.
An LNA at 100mhz seems to me rather pointless and a waste of effort (Not to discourage though its always fun to try!). Loss at this frequency isn't a huge issue and you will be better off focussing on your antenna. I'm going off my guts here I'm not an expert in EME but I can't see it be a necessity.
If you are wanting to get into this, start off by listening into stations. Get yourself a decent SDR radio (lots of fun to be had with these thing) and build yourself a basic EME station. Once you've become an expert in receiving go get a license and and a radio (or build one!) and start trying to communicate! Hopefully by this time you will have discovered all the other opportunities available in amateur radio!
Just my thoughts ;)
-
Yup, this is a documented (if less common) aspect of ham radio. Get a license and you can experiment to your heart's content using the ham bands.
Also look up meteor burst communication. Even just monitoring the ISS passing overhead can be fun. Astronaut hams sometimes pick up the mic and make QSOs with ground stations as well.
-
Pretty cool, but what's really gonna fry your noodle is that they radared Venus from the Earth to find out its rotation period and plane... in 1961.
-
An LNA at 100mhz seems to me rather pointless and a waste of effort (Not to discourage though its always fun to try!).
Plus, 100MHz is right in the middle of the FM broadcast band where transmitter power levels approaching +70dBm are not uncommon. Depending where you are that might be a rather annoying source of interference.
-
I am not a ham but I first heard about moonbounce decades ago from a colleague ee/ham. So old news. I also remember seeing a picture of one of the laser reflectors left by the Apollo missions (11,14,15). Wiki here:http://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment (http://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment)
You don't need a ham license to ping one of those!
-
I think the first EME was looked at in late WW2, as a method of ship data comms, but the crap S/N limits data rate, Shannon limit.
The Ham ticket is not that hard especially if you have a interest in electronics but opens up for experimentation a big chunk of RF spectrum. Local ham clubs are always looking to encourage new hams.
-
If you are wanting to get into this, start off by listening into stations. Get yourself a decent SDR radio (lots of fun to be had with these thing) and build yourself a basic EME station. Once you've become an expert in receiving go get a license and and a radio (or build one!) and start trying to communicate!
Ok, this seems like a reasonable approach.
Below is the list of items suggested in the article for a transmit/receive EME. How would you modify it for "Phase 1 Receive Only" while hopefully being able to reuse some/most? of the investment for "Phase 2 Receive and Transmit"? Thx
1. TRANSCEIVER: Whatever you choose to spend.
2. AMP/PREAMP: Up to $450 new depending on brand; less if purchased used.
3. POWER SUPPLY: Up to $200 for a new linear-type. I paid $105 shipped for a new MFJ switcher (compact, reliable, and there are *NO* noise problems with it!).
4. ANTENNA: $225-$250 including shipping and/or local sales tax (if bought from HRO).
5. TV ROTOR: ~$100.
6. LOW-LOSS COAX: ~$60-$120 depending on type and length.
7. INTERFACE UNIT: $160 for a Rigblaster Plus II.
8. PC/LAPTOP: Whatever you choose to spend.
9. WSJT and Dimension 4 software: FREE
-
You can learn a lot by going to the penultimate Australian EME website of VK3UM...
http://vk3um.com/ (http://vk3um.com/)
Doug has written the excellent program EME calculator, that will allow you to work out the entire path loss/system gain for a two way contact via the moon. Its fun to experiment with different antenna types in it to see what effect it has on the path loss.
He's also written EME Planner, Libration Calculator, and others to assist you in an EME adventure.
Oh and check out the pictures of his 8m dish that's mounted on a Centurion Tank ring gear so he can rotate it!
regards
Tim
-
I think the first EME was looked at in late WW2, as a method of ship data comms, but the crap S/N limits data rate, Shannon limit.
The Ham ticket is not that hard especially if you have a interest in electronics but opens up for experimentation a big chunk of RF spectrum. Local ham clubs are always looking to encourage new hams.
VK5RC - I "ported" your other post into this thread so it's all together, Thanks, EF
---
Hi EF, EME is achievable with home-brew gear, there are quite a few Hams who have EME capable stations.
Probably the easier path is to get your ham ticket which will allow you to transmit a reasonable power level on a frequency where someone else is listening.
Guys like vk3um ve4ma are some of the leaders in the field.
There appears roughly 2 paths, first go for morse or voice level communication which needs a lot better S/N ie more power, better antenna (dish) and better receive path. The other path is to use spread spectrum techniques (computer encoding decoding) using a program eg jt65, S/N can be as low as - 18dB ie below noise and still get decode. This allows medium level eg 100w, modest antennas ie yagis, and little preamp. Activity on 140MHz JT65 ham band is quite active, building a receive only station negates licencing issues. Another area that may interest you is WSPR, another digital mode. Communicating across the globe with 0.1 W is fascinating.
It is an interesting technical 'hobby'.
Regards Rob
-
Looks like vk3um is a leader in EME.
This is very cool (Sample Echo Off The Moon):
http://www.vk3um.com/1296_CW_Feb06.wav (http://www.vk3um.com/1296_CW_Feb06.wav)
But I think I'd need to find an antenna that will fly a little better with the Home Owner's Association:
http://www.vk3um.com/Dish%20Photos.html (http://www.vk3um.com/Dish%20Photos.html)
-
On VHF you can get good EME with just a Yagi antenae. Many people will use 4 coupled together but one on its own will work. Take a look at this site/PDF.
http://tcf.pages.tcnj.edu/files/2013/12/SMALLSTATIONEME.pdf (http://tcf.pages.tcnj.edu/files/2013/12/SMALLSTATIONEME.pdf)
-
You can do EME in any band, most use is 50MHz and up, on 50 till 432MHz you can go for a single yagi, but the most use is 4 yagi's on an H bay, let's say for 50MHz 4x7elements.
If you go for 1.2GHz and up you are better serve with an satellite dish, for making some QSO's the minimum recommended it's 3 meters dish and about 300W on the feed for 1.2GHz.
Just Google for EME station.
-
A reasonable stepping stone is ham radio satellites. If you can't receive those, you'll have a mighty tough time doing EME.
You don't even need an expensive setup, but the lessons drawn from satellites including orbital prediction, weak signal reception, antenna polarisation and doppler can be applied directly to both satellites and EME.
I've done many live demos at ham fests with just an off the shelf handheld radio and hand held yagi. There is a knack to it as with many facets of this kind of thing, it wouldn't be interesting if there wan't some skill to gain.
You can also pick up telemetry from LEOs with just a simple monopole antenna, an SDR and a PC.
Finally, I should warn you about EME. I was lucky enough to be invited to be the after-dinner guest speaker at the annual worldwide EME conference when it was held in Cambridge, UK in 2012. There were a lot of folks there from across the globe, a couple of hundred or so, a lot of whom are pretty seriously into this stuff. If thought collecting exotic test equipment was a reasonably hedonistic way to spend your kids' inheritance, you should see what some of these guys get up to!
-
+1 re HowardLong's comments, but it is a lot of fun and you can do it more cheaply than K4MSG lists but it is a good article. EF Thanks for porting my comments!
I have found Amateur radio a lot of fun as there are different areas you can get an interest in, they do vary after a few years. Also there are a lot of good guys like W2AEW keen and good teachers.
I have posted some photos of parts of my setup. For me this is a hobby and EME has taken me about 18months of my infrequent spare time (job and family) and saving for bits and pieces
Firstly the feed horn, it is an VE4MA super, consisting of 7" stainless steel gas flue pipe and a 16" diameter cake tin ! The G4DDK LNA can be seen, the receive relay is hidden behind. Red is the transmit line, green is receive.
Secondly is the PA, I think it is getting out about 300W at 1296HMz, I bought two of W6PQLs pre made PA s - you can see one standing vertically closest to the camera (not cheap but nice units). You need to split the signal before and then recombine after, see the Hybrid couplers and plumbing on the top surface. It sucks some juice needing 25A at 28V. No magic smoke released yet but no self echo either!
-
I think the first EME was looked at in late WW2, as a method of ship data comms, but the crap S/N limits data rate, Shannon limit.
The Ham ticket is not that hard especially if you have a interest in electronics but opens up for experimentation a big chunk of RF spectrum. Local ham clubs are always looking to encourage new hams.
Just a bit of history - EME was first accomplished in 1946 - a US Army Signal Corp experimental project called Project Diana:
http://en.wikipedia.org/wiki/Project_Diana (http://en.wikipedia.org/wiki/Project_Diana)
It actually paved the way for radio astronomy and even manned space-flight, long range space exploration, etc. (up until then, no one knew of radio signals could penetrate our atmosphere). This project was run out of Camp Evans, part of Fort Monmouth in NJ (less than an hour from my home). The site is now part of a historical site. One of the amateur radio clubs I belong too has their facility in the same building that Diana was operated in. The mounts for the radar antenna that was used are still in the ground outside of the building. Cool stuff!
-
Thanks very much to everyone for the info, enthusiasm, and encouragement.
I'm trying to figure out if EME is feasible given my current state of knowledge and abilities. To figure it out I've made a small initial project outline. Please feel free to insert any answers, info, comments, questions, etc. Thanks!
EME Project
Phase 0 (Feasibility Assessment)
Phase 1 (Receive Only)
• Phase 1A: Receive a terrestrial HAM signal
• Phase 1B: Receive a LEO signal
• Phase 1C: Receive something tougher than a LEO signal but easier than an EME signal? Any need for this step?
• Phase 1D: Receive an EME signal
Phase 2 (Transmit and Receive)
• Phase 2A: Transmit and receive terrestrial HAM signal
• Phase 2B: Transmit and receive a LEO signal
• Phase 2C: Transmit and receive something in between LEO and EME signal? Any need for this step?
• Phase 2D: Transmit and receive an EME signal
Questions (for Phase 0 Feasibility Assessment)
Questions Regarding Phase 1
1. Can the same transceiver and antenna (in receive only mode) be used for Phase 1A and Phase 1B? For example, is it fair to assume that Phase 1A and 1B could both be done with a Yaesu FT-60R (or lesser radio) and a handheld or small tripod mounted antenna?
2. Is there a need for Phase 1C? If so, what is it?
3. What is the lowest cost and/or fastest path to Phase 1D? (What is the recommended configuration for Phase 1D? How much if anything used in Phase 1A and 1B can be reused?) Does it make sense to build a configuration suitable for Phase 1D and use it for Phase 1A and 1B?
4. Key Question: Is it correct that all of Phase 1 can be done (in the U.S.) without a FCC license?
Questions Regarding Phase 2
1. Key Question: What license(s) will be needed for Phase 2?
? Phase 2A: Technician?
? Phase 2B: General?
? Phase 2D: ?
2. What is the recommended incremental configuration for progressing from 2A thru 2D? ie, How much if anything used in Phase 2A and 2B can be reused in 2D? Key Question: What is the smallest antenna that is likely to achieve a successful transmission in Phase 2D? (The neighborhood isn't likely to support anything much more than a portable/temporary tripod mounted antenna; possibly a DirecTV size dish, but nothing larger will fly around here.)
3. In Phase 2A it would seem possible to send and receive my own signal. Can sending and receiving my own signal be done in Phase 2B and 2D, or is the nature of LEO and EME Transmit/Receive such that it is unlikely to receive your own signal? (ie, Are LEO and EME transmissions largely or entirely dependent on someone else confirming receipt of a LEO or EME transmission via a QSO?)
-
First thing first, what band do you plan to do EME, 50, 144, 432MHz, 1.2, 2.4, 5.7, 10GHz?
Then go from here.
-
I'm a licensed ham, but haven't done EME (but have read some about it), so I'll try to limit my answers to those areas where I have some knowledge.
First, getting a license isn't very hard. If you're reading this board, you probably have most of the electronic theory background already, and that's what most candidates find the toughest part. Since you've said you're in the US, I'll go out on a limb here and say that getting a license is the easiest and cheapest part of the journey you're planning (other country's license requirements may be harder). But getting a license does require taking an exam, and taking an exam requires finding a site and time where an exam is offered. After the exam, it will take a few weeks for the paperwork to be processed. So try to get that out of the way ASAP. Go to http://www.arrl.org/getting-licensed (http://www.arrl.org/getting-licensed) and poke around to find out more info. It would be a shame to get to Phase 1D, then start looking for an exam session, and find out that you were a week late for an exam session, and the next one in your area was several months away.
Practice exams are available on-line from various sites. Take a few until you are solidly passing.
Key Question: What license(s) will be needed for Phase 2?
Most EME work is done in the VHF/UHF bands, where a technician has full privileges. So the most basic license will do the trick. However, once you're in an exam session, you can take as many tests as you want for the one fee you paid, until you fail an exam or pass them all. So you might as well try for the general and extra exams while you're there. These license classes open up lots of opportunities on the HF (shortwave) bands, where you can bounce signals off the ionosphere and talk around the world. It's a different niche of Ham radio, but an interesting and popular one.
is it fair to assume that Phase 1A and 1B could both be done with a Yaesu FT-60R (or lesser radio) and a handheld or small tripod mounted antenna?
Phase 1A/1B, and 2A/2B, yes. But it's probably a dead end as far as EME.
The FT-60R is a nice radio, I've got two myself. But it is a low powered FM-only walkie-talkie. Plenty of people use them for satellite communications, with upgraded antennas. You can even talk to the astronauts aboard the ISS, if your timing is just right and you have a bit of luck. But a problem is that it won't send or receive the modes most useful for weak signal work. My understanding is that most EME is done with SSB, Morse, or various digital modes, and an FM-only radio won't do any of that. Someone has probably done EME using FM, but it would require significantly more antenna and power than the other modes. I believe what you want is an all-mode transceiver that covers the bands you're interested in. There are various possibilities here, but I don't know enough to recommend specific makes/models.
There are hams who thrive on a challenge and like to do something most people would call impossible. You could probably get a nice writeup in QST (the ARRL's monthly magazine) if you managed to make an EME contact using an FT-60R. The antenna and amplifier required to accomplish such a feat would not be trivial or inexpensive.
Key Question: Is it correct that all of Phase 1 can be done (in the U.S.) without a FCC license?
Yes, there is no license required for receiving, period. Furthermore, it is legal to own transmitters without holding a license, but it is not legal to transmit with them. So, at least in theory, you could buy a transceiver that you would eventually use for phase 2, even before you got your license. Some sellers might not be eager to sell to you before you were licensed, however.
In Phase 2A it would seem possible to send and receive my own signal. Can sending and receiving my own signal be done in Phase 2B and 2D, or is the nature of LEO and EME Transmit/Receive such that it is unlikely to receive your own signal?
For EME, you are likely to receive your own signal, like it or not. There's a bit more than a 2 second delay for EME round-trip. That's plenty of time for a transceiver to switch from transmit to receive and to begin receiving.
-
The mounts for the radar antenna that was used are still in the ground outside of the building. Cool stuff!
Even in this ARRL Amateur Radio Technician Class Training Course they mentioned EME communication at UHF/VHF and said something about Yagi antenas and... parabolic dishes.
https://www.youtube.com/watch?v=CPyidvTGJ9Y (https://www.youtube.com/watch?v=CPyidvTGJ9Y)
Why parabolic dish is in my interest-that is simple-during the day use it for solar thermal in CSP, but at night if it could be used for radio communication it could be even more fun, so trying to estimate if 3m-5m parabolic dish could be usable for EME? :popcorn:
-
The problem of dual use parabolic dishes is in swapping the hardware out of the focal point, not an insoluble problem though. The dish surface obviously needs to be both rf and light reflective. When you solve it, post your solution. I'd be interested!
Interesting history re eme, my memory was a bit off!
-
First thing first, what band do you plan to do EME, 50, 144, 432MHz, 1.2, 2.4, 5.7, 10GHz?
Then go from here.
That's a fair question but I don't have enough experience to know. My objectives are to make it as easy/practical and cost-effective as possible to bounce a signal off the Moon and hear it come back to Earth. My biggest constraint is that I can't deploy a big antenna. Perhaps some type of small to medium size Yagi will have to do, but no dish is likely to be doable.
Next, as I don't have a license yet, I'd like to go for whatever will minimize licensing (ie, the lesser the license requirement the better).
Other than those considerations, I'm open to whatever frequency (or frequency tradeoffs) you suggest.
-
Been a ham for decades but not very active and never did any EME but read a lot and visited a few 'shacks' that were set up for EME. First know that EME can be a real time and cash sink. You have to figure out what total budget you want to invest then put 50% into the antenna/rotator/low loss feedline and the rest goes into good low noise preamp and then either a transceiver or separate receiver/transmitter. Good challenge and as I said there is a ton of ham reading material available. The best path is if you can find a local 'Elmer' that has first hand experiance to mentor your path. Good luck
EDIT: Getting a U.S ham licence is easier then ever. They dropped all morse code testing requirement and there are on-line practice testing sites for all licence levels. I went from a Technician to Extra class with just a couple of weeks with the practice sessions and then one trip to a local testing session one Saturday.
73
-
First thing first, what band do you plan to do EME, 50, 144, 432MHz, 1.2, 2.4, 5.7, 10GHz?
Then go from here.
That's a fair question but I don't have enough experience to know. My objectives are to make it as easy/practical and cost-effective as possible to bounce a signal off the Moon and hear it come back to Earth. My biggest constraint is that I can't deploy a big antenna. Perhaps some type of small to medium size Yagi will have to do, but no dish is likely to be doable.
Next, as I don't have a license yet, I'd like to go for whatever will minimize licensing (ie, the lesser the license requirement the better).
Other than those considerations, I'm open to whatever frequency (or frequency tradeoffs) you suggest.
As you may have surmized, there are a LOT of tradeoffs. Antenna size scales inversely with operating frequency. Path loss depends highly (and non-linearly) on operating frequency. etc. etc.
There are quite a few EME enthusiasts in the amateur radio community. I know a few guys that are really into EME, and most are operating at 432MHz or above.
If you would like to learn more, you might want to view some of these example pages that I found with a simple search:
Moonbouncers Information website: http://www.moonbouncers.org/ (http://www.moonbouncers.org/)
EME Newletter archives by K2UYH: http://www.k2uyh.com/news.htm (http://www.k2uyh.com/news.htm)
The 144MHz EME Newsletter: http://www.df2zc.de/newsletter/ (http://www.df2zc.de/newsletter/)
Info on mostly 6m EME operation: http://www.bigskyspaces.com/w7gj/ (http://www.bigskyspaces.com/w7gj/)
-
AG6QR - Thanks.
I'm up for taking the test and I'm pretty sure with some study I can pass the first one, not sure yet about the second. What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project.
It seems from the reading I've done so far that some sort of digital transmission might have a better chance of succeeding - I'm still very early in figuring out this stuff.
As mentioned, I'm limited by the size of antenna I can deploy - I'm in a neighborhood where small and unobtrusive is kind of a requirement. So, maybe I need to work backward from what antenna will be politically acceptable around here. From there I can figure out what that leaves in terms of transmit/receive frequencies, and how much power is needed from the PA and what sort of LNA will work, and maybe from there what sort of modulation. Kind of a goofy set of constraints driven by Home Owners Association considerations but it is what it is (the neighbors are very nice, they're just not into big antennas).... so maybe something among SSB, Morse, or something digital.
If the FT-60R stands no chance of doing EME I might be able to go for a mobile/portable or desktop type transceiver that will ultimately power Phase 2D but use it for Phase 1 (receive only) as you suggest.
I'm pretty sure the delay from Earth to Moon and back has to be at least a couple seconds. In standard Geosynchronous satellite communications the delay up to a satellite and back down is about 270 milliseconds and GeoSats are only about a tenth of the way to the Moon. Even so with a 2-3 second delay it would seem tricky to be continuously transmitting on one frequency and then trying to tune to another frequency to catch an iffy transmission. Maybe this would require one transceiver or transmitter for send and another transceiver or receiver for monitoring/receiving?
-
eneuro - I'm betting a parabolic dish antenna would be a good choice; it won't work for me because of my neighborhood setting but I think you should pursue it if you can. It would be great if we could get a few experimenters as well as experienced advisors and others to give it a go. We might need some similar but different approaches depending on everyone's interests and requirements.
-
First know that EME can be a real time and cash sink. You have to figure out what total budget you want to invest then put 50% into the antenna/rotator/low loss feedline and the rest goes into good low noise preamp and then either a transceiver or separate receiver/transmitter.
Yep, that's one of the key reasons I'm in the Phase 0 (Feasibility Assessment) step.
-
As you may have surmized, there are a LOT of tradeoffs. Antenna size scales inversely with operating frequency. Path loss depends highly (and non-linearly) on operating frequency. etc. etc.
Roger that - it's all a "link budget" for sure. Seems like I have to stick with a modest size antenna, which I think may dictate frequency, amp, and LNA considerations. After the RF section we get to what type of signal is going to ride on the RF. It's probably an iterative process. I'm open to whatever the good Moon guides here might suggest. Once I can itemize what the overall system looks like I can see if there is a sufficient "business case".
PS, I've said it before and I'm happy to say it again, and again. Your teaching videos are fantastic. It's an honor to receive your advice. Thanks
-
What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project.
Yes, the entry level Technician allows full allowed output power (1,000 watts) on any ham band from 50Mhz on up.
-
What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project.
Yes, the entry level Technician allows full allowed output power (1,000 watts) on any ham band from 50Mhz on up.
Cool, Technician Class is doable (knock on wood) :-+
Now we're down to finding an antenna that blends in with the neighborhood, the rest of the configuration, and the budget :)
-
What I'm not clear about is whether the first license ("Technician") is going to enable me to transmit with the required frequency and power configuration (all still TBD) for the full EME transmit receive project.
Yes, the entry level Technician allows full allowed output power (1,000 watts) on any ham band from 50Mhz on up.
Actually, full legal limit for VHF and above is 1500Wpep, and all possible for a Tech licensee in the U.S.
-
You can learn a lot by going to the penultimate Australian EME website of VK3UM...
Why would you rate his site the second to last?
-
You lucky buggers, we get 400W max and if eirp over a certain amount we have to do and keep copies of safety calculations! Nice calculator on vk3um website.
EF re the license, I don't think it will be difficult, gee I passed! HiHi.
If you can find a local ham club, they do the exam usually and can be a great resource for gear and know how.
-
Ok, after reflecting (no pun intended for this EME project) on the replies posted here it seems like the initial article I tripped across might have been reasonably on the mark:
http://www.k4lrg.org/Projects/K4MSG_EME/ (http://www.k4lrg.org/Projects/K4MSG_EME/)
The design calls for:
144 MHz SSB (this falls in the realm of 2 Meters?)
recommends a high stability reference oscillator (something I've been thinking about for another project); I think to be an EEVer you have to be at least a little project hungry :)
Yagi antenna (14.5' boom is pushing it on my aesthetics constraint but maybe it can be set up and taken down reasonably easily on a tripod)
Power Amp (150 watts?), preamp/LNA, and power supply designed to be somewhat portable/temporary
Transceiver (suggested Icom IC-706MkIIG)
What I'm still not clear about with this design is whether K4MSG has been able to hear his own signal comeback from the Moon or whether this design requires him to receive "QSOs" from other listeners around the world. He does point out that "when you are running a single-Yagi, low-power station for EME you cannot expect to successfully achieve two-way communications via the Moon except under the best of conditions." Perhaps with a bit more resource thrown at the design it might be possible to send and receive your own transmission?
If anyone has any comments on how to enhance/improve K4MSG's design I'm open to suggestions - but it looks like a pretty good starting point.
Still not sure about exactly what the preferred signal type is to try to bounce off the Moon in order to be able to clearly confirm it was a specific signal that hit the Moon and came home... Maybe tones of some type?
This seems like a pretty definitive type of signal:
http://www.vk3um.com/1296_CW_Feb06.wav (http://www.vk3um.com/1296_CW_Feb06.wav)
-
Ah, John and Martha King. I did not know they did ham training classes. They are very well known in the pilot community for their pilot training videos. I think I sat through 12 hours of them on VHS once for my private certificate. They are so thorough and boring, that you just want them to go faster. :-)
The mounts for the radar antenna that was used are still in the ground outside of the building. Cool stuff!
Even in this ARRL Amateur Radio Technician Class Training Course they mentioned EME communication at UHF/VHF and said something about Yagi antenas and... parabolic dishes.
https://www.youtube.com/watch?v=CPyidvTGJ9Y (https://www.youtube.com/watch?v=CPyidvTGJ9Y)
Why parabolic dish is in my interest-that is simple-during the day use it for solar thermal in CSP, but at night if it could be used for radio communication it could be even more fun, so trying to estimate if 3m-5m parabolic dish could be usable for EME? :popcorn:
-
You can learn a lot by going to the penultimate Australian EME website of VK3UM...
Why would you rate his site the second to last?
My bad use of an adjective, should have been "ultimate"
regards
Tim
-
Be a bit careful with a IC706 as an IF rig prior to other gear eg transverters, it's a great general rig (i own one) but it uses - ve feedback for power control, so it can give a spike at higher power before settling. For transverter use the yaesu ft817 is popular.
-
You lucky buggers, we get 400W max and if eirp over a certain amount we have to do and keep copies of safety calculations! Nice calculator on vk3um website.
EF re the license, I don't think it will be difficult, gee I passed! HiHi.
If you can find a local ham club, they do the exam usually and can be a great resource for gear and know how.
Yes, the US exam for a technician is not difficult.
My local club has a 10-year-old who has held his technician license since he was 8. He's about to be joined by another 10 year old who will be taking the test shortly. Based on my conversations with second kid, I'm very confident he's going to pass. Yes, both of these kids are bright, but I think most 10-year-olds are bright enough to get a license if they want to. Most of them take harder tests in school already. The thing that's most unusual about these kids is that they have the motivation and interest to study for this test. Of course they have parents who are hams, too.
It does bother me somewhat that an eight year old has the legal authorization to go beaming a kilowatt and a half of RF energy around. That seems crazy. But that's the way the rules are written here. In the particular cases I know, mom and dad limit kids to 5w handhelds, or occasional 50 watt mobile, and the kids are very well supervised.
-
I'm pretty sure the delay from Earth to Moon and back has to be at least a couple seconds. In standard Geosynchronous satellite communications the delay up to a satellite and back down is about 270 milliseconds and GeoSats are only about a tenth of the way to the Moon. Even so with a 2-3 second delay it would seem tricky to be continuously transmitting on one frequency and then trying to tune to another frequency to catch an iffy transmission. Maybe this would require one transceiver or transmitter for send and another transceiver or receiver for monitoring/receiving?
Yeah, the delay is around 2.5 seconds, or thereabouts. It's roughly a 384,000 km, * 2 for a round trip, or 768,000 km round trip, divided by the speed of light, 300,000 km/s.
When working a manmade satellite, the uplink frequency is deliberately separated from the downlink frequency. But for EME, the frequency doesn't change as you bounce a signal off the moon, except for a slight change due to doppler effect. But the doppler effect isn't large, because the distances aren't changing rapidly. It's hard to make a receiver selective and sensitive enough to receive well when it has a nearby powerful transmitter transmitting at very nearly the same frequency it's trying to listen to. So simultaneous transmission and reception of moonbounce at one site using one antenna is pretty much out of the question. But you don't need to do simultaneous transmission and reception to hear your own signal. If you transmit for two and a half seconds or less, you can listen to your echo come back. If you transmit for longer, you'll hear the last two and a half seconds of your transmission.
For making longer transmissions, yeah, it's easier if the transmitter and receiver are far enough apart that the receiver doesn't hear the transmitted signal directly, but only hears it via moon bounce.
-
I'm pretty sure the delay from Earth to Moon and back has to be at least a couple seconds. In standard Geosynchronous satellite communications the delay up to a satellite and back down is about 270 milliseconds and GeoSats are only about a tenth of the way to the Moon. Even so with a 2-3 second delay it would seem tricky to be continuously transmitting on one frequency and then trying to tune to another frequency to catch an iffy transmission. Maybe this would require one transceiver or transmitter for send and another transceiver or receiver for monitoring/receiving?
Yeah, the delay is around 2.5 seconds, or thereabouts. It's roughly a 384,000 km, * 2 for a round trip, or 768,000 km round trip, divided by the speed of light, 300,000 km/s.
When working a manmade satellite, the uplink frequency is deliberately separated from the downlink frequency. But for EME, the frequency doesn't change as you bounce a signal off the moon, except for a slight change due to doppler effect. But the doppler effect isn't large, because the distances aren't changing rapidly. It's hard to make a receiver selective and sensitive enough to receive well when it has a nearby powerful transmitter transmitting at very nearly the same frequency it's trying to listen to. So simultaneous transmission and reception of moonbounce at one site using one antenna is pretty much out of the question. But you don't need to do simultaneous transmission and reception to hear your own signal. If you transmit for two and a half seconds or less, you can listen to your echo come back. If you transmit for longer, you'll hear the last two and a half seconds of your transmission.
For making longer transmissions, yeah, it's easier if the transmitter and receiver are far enough apart that the receiver doesn't hear the transmitted signal directly, but only hears it via moon bounce.
Excellent - this is what I was looking for, now I just need to understand it :)
Seriously, what I think you pointed out was:
1) Unlike a manmade satellite that has a transponder receiver and a transponder transmitter which operate on different frequencies EME is just passively bouncing the signal off the Moon so there is no frequency change.
2) But further to your point it's hard to make the receiver selective and sensitive enough to receive well when the system is transmitting at the same or nearly the same frequency (given the modest Doppler effect that occurs in a very short period).
So given that, is the process one of transmitting for a short defined period of time (like 2.5 seconds) and then shutting off the transmission to listen for the signal coming back? If so, is this done by hand with a stop watch or can the transmission be computer controlled to manage the on/off interval? Does this mean that signals are limited to the 2.5 second duration? (I thought I heard a longer signal message in this: http://www.vk3um.com/1296_CW_Feb06.wav (http://www.vk3um.com/1296_CW_Feb06.wav) ? Maybe there is something fundamentally different going on here?)
On a different topic, what are the tradeoffs between VHF/UHF and HF for EME? Looks like WSJIT-X uses JT9 for HF and gives 2dB more sensitivity with only 10% of the bandwidth of JT65A. What is the practical advantage of using less bandwidth - less likely to hit interference, or something else?
Or is there an advantage to using JT65 with VHF/UHF? (Smaller antenna?)
Then there's WSJT-X "bi-lingual mode" that supports JT65 and JT9 - maybe this is the winner (and the frequency decision is a separate decision)?
Thanks, EF
-
How about a rope yagi, you put it up when you want it then take it down afterwards, If your negbours complain tell them its a washing line.
http://www.bigskyspaces.com/w7gj/longyagi.htm (http://www.bigskyspaces.com/w7gj/longyagi.htm)
-
The problem of dual use parabolic dishes is in swapping the hardware out of the focal point, not an insoluble problem though. The dish surface obviously needs to be both rf and light reflective.
Dish and feed for 1296 MHz (23cm) from this link http://www.ok1dfc.com/peditions/ymk2012/dl1ymk2012.htm (http://www.ok1dfc.com/peditions/ymk2012/dl1ymk2012.htm)
(http://www.ok1dfc.com/peditions/ymk2012/dish23.JPG)
Probably it is smaller than 3m, however I'd like make my parabolic dishes for CSP using fiberglass mold and glue inside hundreds of triangle mirrors, so unsure if small gapes between mirrors will affect somehow reflection of those 23cm/70cm radio waves :-\
Something like this below comes from my CAE and ~15cm mirror triangles were entered there and system divided whole 3m dish to cover it automatically, so now it is possible output CNC G-code to cut needed mirrors and also output STL 3D dish geometry to make molds needed for fiber glass.
https://www.youtube.com/watch?v=zpoUGfqmNnw (https://www.youtube.com/watch?v=zpoUGfqmNnw)
Those 15cm triangles will be of course good for solar thermal CSP, but I have no idea what happends when I will try reflect 432Mhz (70cm) or 1296 MHz (23cm) radio waves-maybe it could work with 10GHz (3cm).
If this surface were solid probably it could work, however more knowledge needed how those "umbrella" dishes for EME are made-some kind of netting like for satelite transparent dishes to let them operate at stronger winds regardless of huge diameter disk?
-
Those 15cm triangles will be of course good for solar thermal CSP, but I have no idea what happends when I will try reflect 432Mhz (70cm) or 1296 MHz (23cm) radio waves-maybe it could work with 10GHz (3cm).
If this surface were solid probably it could work, however more knowledge needed how those "umbrella" dishes for EME are made-some kind of netting like for satelite transparent dishes to let them operate at stronger winds regardless of huge diameter disk?
I have some experience on making dishes for 23cm and 13cm (1296 and 2300/2400MHz) but this was 15 years ago,during the days of the AO-40 satellite which was in an elliptical orbit with apogee at about 60,000km (to give you an idea of what's achievable, you could hear and just about decode the FEC telemetry at apogee with either a simple monopole or a patch antenna at 2.4GHz).
There are a number of mechanical engineering issues, mostly to do with weight and wind load. You can make a reasonably good parabola by stressing spars much like an umbrella, however it should be noted that to keep the shape reasonably parabolic, you may need to have a fairly shallow dish, so that will affect the f/D can making the feed point distance quite long, meaning you need to take care with the feed to illuminate the dish sufficiently. Over-illumination means you're going to receive ground noise from behind the dish. Under-illumination means you're wasting some of that valuable antenna real estate. For transmit, a -10dB taper at the edges is a reasonable rule of thumb but for receive -20dB might be more appropriate to reject ground noise. This is one of the few times where antenna reciprocity doesn't always work!
The general synopsis is that you're aiming for aberrations away from a parabola of less than lambda/10, and the same applies to the use of any mesh used for the reflector. Small aperture (~1cm) chicken wire works, but it's surprisingly heavy, however it does reduce wind load to some degree. Aluminium fine mesh is light weight but the fluid dynamics means that wind load will be high, almost as bad as a solid dish. There is a school of thought which says that mesh lets in noise from behind the dish, I don't know if that's the case, I am sure that someone will have some info on that.
You will also need to consider how to mount and move the dish mechanically.
-
I used a 3m diameter satelite dish , which comes with reasonable ability for azimuth movement, and a bit of bodging made for elevation control. I used two satellite actuators. The dish mount (it is mobile! as I have to use it in my driveway!) is a modified engine support/frame with extension spars.
I have generally found one of the easiest and best methods is to find a popular (i.e. cheap) product and modify it for your needs. Building something from scratch will cost a lot more in dollars and time.
-
This is my 2 cent opinion,
I belive 2m band (144Mhz) is good start point why :
1. the size of antena is "manageable"
2. the cost for accesories (LNA, down converter, Antenna switch, PA) is fair enough
3. The activity is among the EME enthusiats is good
I will not suggest to try EME with a wet string type station but many-many report with 12 element single yagis can made some 2 way contact and if You can not transmit cause You do not have licence maybe You can contact some "big gun station" like W5UN, DG9MAQ (germany), VK3GY(Australia) and many more to made schedule to try to listen to them.
if I start again from zero my EME station here list I like to have (remember this is a list for 2 way contact)
1. Decent HF transceiver like TS850, FT950, etc
2. Down converter (antenna mount style with LNA)
3. Low loss cable like heliax LDF5
4. 1Kw Solidstate PA
5. Antena switch relay with sequencer
6. 2 X 12 Element optimized yagis (K1FO etc or You can buy from cushcraft, M12 etc)
7. PC for sofware logging, Moon Position, cluster monitor)
seem many thing but honestly in my Country with almost 300 milion people there is no more than handfull people can hear their sound whats like after travel 600,000km away. :-//
-
A couple random points:
I agree that 2M is the way to go. The 2M band is very straightforward for new hams, and the antenna sizes are reasonable. Also, you can use your radio to talk on local repeaters and such, which is important for building all of your other ham skills and knowledge.
To study for the exam, I highly recommend buying The ARRL Ham Radio License Manual. It's currently listed at $27 on Amazon. Yes you can study for and get the license without buying any book. Heck, they post the entire question bank with answers online to study from. However, to me the tech exam is not just about getting your license, but also learning. The ARRL license manual does a great job of teaching many important concepts.
-
Ok, if you wish to do EME, you should start by subscribing to this list and listening about two weeks before you post. You need to do that to understand the culture of the list.
The LIST is HIGHLY MODERATED, moderated to a level that most EEV users would never stand for. And it is moderated that way for good reason due to the high level of technical discussion that occurs. Beginners are welcome, but it is NOT a general ham radio chat, its VHF and above, and a few seti and satellite monitoring guys also post. Non-hams just looking for entertainment would generally be asked to be "monitor only". All posts are highly moderated, and off topic stuff just vanishes. Wasting the moderators time is well, probably highly to very fatal to your list access.
To give you an idea of the level of sophistication, when these guys have a conference, Rhode and Schwartz or Agilent usually send two sales guys and a few 100,000$ instruments on loan for noise figure measurement.
You can see anything from the best waterproofing for an outdoor connector to subtle errors being found in Y-Factor noise measurement papers. Some of these folks build systems at 78 to 120 Ghz and go mountain-topping with them. Others consider wire bonders in the basement a minimum level of tooling. Others just go out with two modified radar detectors and have some short range fun. :-)
http://lists.eclectechs.com/cgi-bin/mailman/listinfo/microwave (http://lists.eclectechs.com/cgi-bin/mailman/listinfo/microwave)
The archives are golden.
The list would help you find a EME capable ham near you...
Steve
-
Regarding the exams, the technical side really is pretty simple for your average EE, just do a bit of brushing up using example papers and you should be sweet. Not so easy are the regulations, and you need to know them, and unlike the technical side they're pretty much a memorising thing regrettably. Personally, with those sorts of things I find it easiest to read a text on the subject and then do a couple of dozen example test questions, referring back to the text when I'm unsure. Reiterate the test until you're achieving 100% (or whatever your target is). While it may seem like a chore, most hams are fiercely defensive of their bands and take pride that they have gone through a couple of hoops to gain the right to use them.
There are a few non-hams who don't seem to think it's necessary to go through those hoops, and enjoy their lives indulging in spectrum abuse. As a ham myself, I find it a little irksome as the exams are not exactly hard, I did them when I was 16, passed the technical side with distinction, and got a credit on the regulations. This was on the full exam, not the introductory levels we have now, so if a 16 yo can do that, it can't be that difficult!
There are a few things that you may find irrelevant, in particular HF propagation. I think if I had to take the exams again I'd not do well in that section as I've only transmitted on HF about half a dozen times! Almost everything I do is at VHF and above.
-
So given that, is the process one of transmitting for a short defined period of time (like 2.5 seconds) and then shutting off the transmission to listen for the signal coming back? If so, is this done by hand with a stop watch or can the transmission be computer controlled to manage the on/off interval? Does this mean that signals are limited to the 2.5 second duration? (I thought I heard a longer signal message in this: http://www.vk3um.com/1296_CW_Feb06.wav (http://www.vk3um.com/1296_CW_Feb06.wav) ? Maybe there is something fundamentally different going on here?)
That's a nice recording, and it illustrates the concept well. The high pitched clear sounds, at low volume, are the transmitted morse code. The lower pitched sounds with a little bit of noise behind them are the received code. He transmits a couple of letters, and then waits to hear them come back. Note the pitch changes, probably due to doppler. The echo comes back about two and a half seconds after the original transmission, according to my wristwatch.
Notice he can't send his entire call sign in one go. He breaks it up into chunks of a couple of letters at a time.
-
So given that, is the process one of transmitting for a short defined period of time (like 2.5 seconds) and then shutting off the transmission to listen for the signal coming back? If so, is this done by hand with a stop watch or can the transmission be computer controlled to manage the on/off interval? Does this mean that signals are limited to the 2.5 second duration? (I thought I heard a longer signal message in this: http://www.vk3um.com/1296_CW_Feb06.wav (http://www.vk3um.com/1296_CW_Feb06.wav) ? Maybe there is something fundamentally different going on here?)
That's a nice recording, and it illustrates the concept well. The high pitched clear sounds, at low volume, are the transmitted morse code. The lower pitched sounds with a little bit of noise behind them are the received code. He transmits a couple of letters, and then waits to hear them come back. Note the pitch changes, probably due to doppler. The echo comes back about two and a half seconds after the original transmission, according to my wristwatch.
Notice he can't send his entire call sign in one go. He breaks it up into chunks of a couple of letters at a time.
Yes, it is simple and clear but when you think about what's involved and what is happening it's very inspiring! So just to confirm, even this example is one in which the transmission duration doesn't / can't exceed the round trip propagation time (about 2.5 seconds) - otherwise the outgoing signal would be stomping on the incoming signal, correct?
So - it does seem possible for an EME transmitter to receive his own signal without hoping that someone else hears it and reports it, correct?
If the answer to both is yes, this would be the functionality I'd like to duplicate. :-+ The objective is getting clear, so it's now down to the design and determining if it's feasible to get from here to there, literally and figuratively. :)
-
I used a 3m diameter satelite dish , which comes with reasonable ability for azimuth movement, and a bit of bodging made for elevation control.
This dish was designed exactly for EME or reused from something else?
It looks like it has ~1m focus, so f/D~0.3. What could be focus length in this instalation?
I had 1m in designed CSP, while wanted to optimize for balance and keep center of mass close to the middle of the dish in solar CSP.
Anyway, without reflectors in focus (like in radiotelescopes), no chance to reuse this CSP dish for RF, while for radio in many dish instalations I see those quite huge (probably at least 1 feet long) cylinder hardware boxes, so they probably won't be able easy exchange CSP with this EME equipment, so for the moment could only try to experiment with cheapy 433.92MHz RF modules (close frequency to 70cm EME) like those below I've in hands now, to see if 3m CSP dish will work as more directional antenas with those dongles and maybe could help extend its range >:D
http://www.icstation.com/433mhz-transmitter-receiver-arduino-project-p-1402.html (http://www.icstation.com/433mhz-transmitter-receiver-arduino-project-p-1402.html)
(http://www.icstation.com/images/middle/productimages/1402/1402.JPG)
So, probably will chose f/D for my 3m parabolic mirror in the range 1/3 (1m focus) since it fits my CSP solar power system requirements and later will try RF with this instalation by removeing temprary CSP concentrator 8)
There is sun tracker software, so writing a few lines of code to support moon tracking shoudn't be a problem since this CSP can see the sun covered by clouds to better respond to rapid radiation changed by local small clouds coverage ;)
-
Regarding the exams, the technical side really is pretty simple for your average EE, just do a bit of brushing up using example papers and you should be sweet. Not so easy are the regulations, and you need to know them, and unlike the technical side they're pretty much a memorising thing regrettably. Personally, with those sorts of things I find it easiest to read a text on the subject and then do a couple of dozen example test questions, referring back to the text when I'm unsure. Reiterate the test until you're achieving 100% (or whatever your target is). While it may seem like a chore, most hams are fiercely defensive of their bands and take pride that they have gone through a couple of hoops to gain the right to use them.
There are a few non-hams who don't seem to think it's necessary to go through those hoops, and enjoy their lives indulging in spectrum abuse. As a ham myself, I find it a little irksome as the exams are not exactly hard, I did them when I was 16, passed the technical side with distinction, and got a credit on the regulations. This was on the full exam, not the introductory levels we have now, so if a 16 yo can do that, it can't be that difficult!
There are a few things that you may find irrelevant, in particular HF propagation. I think if I had to take the exams again I'd not do well in that section as I've only transmitted on HF about half a dozen times! Almost everything I do is at VHF and above.
Howard and everyone, thanks for the encouragement on the license test. I'm pretty sure I can get through the theory and test. I'm not so sure if I can get from the test through the actual design process (even though there are a fair number of "templates" around) and especially through the build process. I have a lot respect for the knowledge and skill and experience members here and others have accumulated. I'm certain it's easier to watch the NBA than play in the NBA :)
I'm going to remove the license test from the list of key concerns in the feasibility assessment. Next is the antenna design and size. It has to be neighborhood politically correct. Once I get that figured out and the associated RF design and the overall costs I can see if this is viable in my situation - but I hope others here might give it a go regardless of what I wind up doing. If I had a place to install a 3 meter dish I have a hunch it might be a better way to go... but it's just a guess, I'm still researching. Thanks very much to all the contributors on this thread.
-
A couple random points:
I agree that 2M is the way to go. The 2M band is very straightforward for new hams, and the antenna sizes are reasonable. Also, you can use your radio to talk on local repeaters and such, which is important for building all of your other ham skills and knowledge.
To study for the exam, I highly recommend buying The ARRL Ham Radio License Manual. It's currently listed at $27 on Amazon. Yes you can study for and get the license without buying any book. Heck, they post the entire question bank with answers online to study from. However, to me the tech exam is not just about getting your license, but also learning. The ARRL license manual does a great job of teaching many important concepts.
2 Meter is currently my leading candidate. How small can the antenna be and still have a solid chance of working for EME in your assessment?
I'll give the AARL manual a go. Between the manual, the video(s), and all the articles on the Web it won't be for a lack of information if I can't pass the test :palm:
-
Ok, if you wish to do EME, you should start by subscribing to this list and listening about two weeks before you post. You need to do that to understand the culture of the list.
The LIST is HIGHLY MODERATED, moderated to a level that most EEV users would never stand for. And it is moderated that way for good reason due to the high level of technical discussion that occurs. Beginners are welcome, but it is NOT a general ham radio chat, its VHF and above, and a few seti and satellite monitoring guys also post. Non-hams just looking for entertainment would generally be asked to be "monitor only". All posts are highly moderated, and off topic stuff just vanishes. Wasting the moderators time is well, probably highly to very fatal to your list access.
To give you an idea of the level of sophistication, when these guys have a conference, Rhode and Schwartz or Agilent usually send two sales guys and a few 100,000$ instruments on loan for noise figure measurement.
You can see anything from the best waterproofing for an outdoor connector to subtle errors being found in Y-Factor noise measurement papers. Some of these folks build systems at 78 to 120 Ghz and go mountain-topping with them. Others consider wire bonders in the basement a minimum level of tooling. Others just go out with two modified radar detectors and have some short range fun. :-)
http://lists.eclectechs.com/cgi-bin/mailman/listinfo/microwave (http://lists.eclectechs.com/cgi-bin/mailman/listinfo/microwave)
The archives are golden.
The list would help you find a EME capable ham near you...
Steve
Roger all that. Tech talk only, primarily in receive-only mode. Thanks!
-
Hi
just my 2 cent if you live in urban zone ,not put to much money on system before evaluate first your background noise
start by put yagi antenna pointed vertically to the sky ,mesure noise then swap antenna by a dummy load
if more that 10db difference forgot about it to mutch noise for be usable as location
this was also a really good toll for virtually build a station http://www.vk3um.com/eme%20calculator.html (http://www.vk3um.com/eme%20calculator.html) ,that assume low noise location
on my side i have 2 x 15 feet long Beam in VHF whit elevation azimuth tracking and legal limit power amp ,whit 0.122db noise figure preamp
but urban noise (plasma TV , ethernet over power line etc etc , make my system not able to listen anything even the french grave radar
so for make contact need to be in both direction if you cannot listen forgot it it wort noting ...
Best 73 VE2OLM
-
so for make contact need to be in both direction if you cannot listen forgot it it wort noting ...
Is it posible to make those EME without such big ass parabolic dish antenas from the link to the EME calculator page ?
http://www.vk3um.com/Dish%20Photos.html (http://www.vk3um.com/Dish%20Photos.html)
http://www.vk3um.com/Kennedy%20Spec.pdf (http://www.vk3um.com/Kennedy%20Spec.pdf)
(http://s11.postimg.org/4h2ebwg0f/28_foot_Kennedy_Dish.jpg) (http://postimg.org/image/4h2ebwg0f/)
Wow, 8.5m dish 3.65 focus and f/D~0.43 8)
8 times bigger perpendicular area than small 3m parabolic :popcorn:
-
Hi
today digital mode like JT65 you may make it whit 2 x 15 feet long VHF yagi and 600W
whit 4 of those antenna and 1 Kw you hear your own echo ,assuming you use small bandwidth reveicer ( my SDR one may go down to 1.3Hz bandwidth )
those dish was mostly for 1,2GHZ were power amp > 300W was hard to find so it use dish for increase gain
on VHF was easy to find SSPA up to legal limit so antenna gain may bit less ,but again that assume you have absolutely no in-band noise coming form urban electronic
as example i modelise my antenna 2 x 9 element 15 feet long ,very directive on VHF ,but look lime perfect omnidirectional @ 102.1MHZ were have 25MW FM radio station
this strong signal mix into air whit other that make broadband noise ,so walever my antenna was directional in VHF it pick-up FM radio station even if point to cold sky :rant:
but also for EME bigger is better for antenna so if your wife let you install a 30 foot dish lest go O0
but most common VHF antenna ther day was 4 x 12 to 4 x 20 element long (LFA) beam ,still have some giant array but not really need anymore for digital mode
have fun
-
Hi
just my 2 cent if you live in urban zone ,not put to much money on system before evaluate first your background noise
start by put yagi antenna pointed vertically to the sky ,mesure noise then swap antenna by a dummy load
if more that 10db difference forgot about it to mutch noise for be usable as location
this was also a really good toll for virtually build a station http://www.vk3um.com/eme%20calculator.html (http://www.vk3um.com/eme%20calculator.html) ,that assume low noise location
on my side i have 2 x 15 feet long Beam in VHF whit elevation azimuth tracking and legal limit power amp ,whit 0.122db noise figure preamp
but urban noise (plasma TV , ethernet over power line etc etc , make my system not able to listen anything even the french grave radar
so for make contact need to be in both direction if you cannot listen forgot it it wort noting ...
Best 73 VE2OLM
I can not agree more,
EME is serious bussines maybe the best thing before spend any dollar for anything try to located local HAM club and ask them about EME station in Your local area so You can learn directly from them.
For me take EME for first step into HAM world is HUGEEEEE step not Imposible but hardway
-
Hi
just my 2 cent if you live in urban zone ,not put to much money on system before evaluate first your background noise
start by put yagi antenna pointed vertically to the sky ,mesure noise then swap antenna by a dummy load
if more that 10db difference forgot about it to mutch noise for be usable as location
this was also a really good toll for virtually build a station http://www.vk3um.com/eme%20calculator.html (http://www.vk3um.com/eme%20calculator.html) ,that assume low noise location
on my side i have 2 x 15 feet long Beam in VHF whit elevation azimuth tracking and legal limit power amp ,whit 0.122db noise figure preamp
but urban noise (plasma TV , ethernet over power line etc etc , make my system not able to listen anything even the french grave radar
so for make contact need to be in both direction if you cannot listen forgot it it wort noting ...
Best 73 VE2OLM
Alphatronique,
This is very good advice - this probably should be among the very first operational steps in the process. Might as well check the noise first. Thanks! EF
-
This is my 2 cent opinion,
I belive 2m band (144Mhz) is good start point why :
1. the size of antena is "manageable"
2. the cost for accesories (LNA, down converter, Antenna switch, PA) is fair enough
3. The activity is among the EME enthusiats is good
I will not suggest to try EME with a wet string type station but many-many report with 12 element single yagis can made some 2 way contact and if You can not transmit cause You do not have licence maybe You can contact some "big gun station" like W5UN, DG9MAQ (germany), VK3GY(Australia) and many more to made schedule to try to listen to them.
if I start again from zero my EME station here list I like to have (remember this is a list for 2 way contact)
1. Decent HF transceiver like TS850, FT950, etc
2. Down converter (antenna mount style with LNA)
3. Low loss cable like heliax LDF5
4. 1Kw Solidstate PA
5. Antena switch relay with sequencer
6. 2 X 12 Element optimized yagis (K1FO etc or You can buy from cushcraft, M12 etc)
7. PC for sofware logging, Moon Position, cluster monitor)
seem many thing but honestly in my Country with almost 300 milion people there is no more than handfull people can hear their sound whats like after travel 600,000km away. :-//
The K1FO looks good - let's make this the default candidate - anyone want to suggest an alternative? Thx
-
Potentially depressing info here :palm: But as they say "it's never as good or as bad as it seems" - so we're still just collecting info...
However, if this is correct, while a single small Yagi can receive someone else's EME signal, it might take 4?! Yagi's (not to mention a KW amplifier) to "consistently be able to hear your own echo's under optimal conditions."
http://k7xc.tripod.com/id19.html (http://k7xc.tripod.com/id19.html)
"From what I can gather so far a station running around 800 Watts into 4 Antennas should hear his own echoes some of the time, depending on conditions."
"A typical 2M EME station consists of 4 yagis at least 3 Wavelengths in length fed in phase with a KW transmitter output and preamp with less than 1 DB of Noise Figure and 20 DB gain. Setup as above you should consistantly be able to hear your own echo's under optimal conditions."
This isn't the end of the word or the project but it takes a bit of the bloom off the rose if the EME system requires QSO confirmation from someone else vs. being able to receive your own signal. Maybe there is a middle ground design with less antenna with which you can still receive your own signal but maybe not as consistently?
-
http://www.bigskyspaces.com/w7gj/6mTable.htm (http://www.bigskyspaces.com/w7gj/6mTable.htm)
Antenna spreadsheet heaven (download Excel spreadsheet)
- current assessment: with 1 small yagi you can transmit and hear signals but probably not your own, with 2 yagis it's TBD, with 4 yagi's you stand a reasonable chance of hearing your own signal. Probably need a mult-yagi with cross-polarization to hear your own signal - this will increase size (installation space) requirements, mounting hardware requirements, and complexity.
http://www.newsvhf.com/2m-yagis.html (http://www.newsvhf.com/2m-yagis.html)
http://www.m2inc.com/index.php?ax=amateur&pg=83 (http://www.m2inc.com/index.php?ax=amateur&pg=83)
This antenna has great gain and G/T specs - only challenge is that it has a 55' boom and 21' elements and needs a turn radius of 29' - it's becoming clear why not everyone is bouncing signals off the moon, or at least not bouncing them and hearing their own signal :)
It's starting to look like to be an EME'er you need not only technical prowess, but a pretty decent budget, AND some acres of land.
-
HI
forgot those 21 element antenna did you seriously think that you may manage azimuth elevation whit 55" boom antenna ;-)
that wly most people use 2 or 4 smaller antenna that was more manageable ,even if my setup was 2 x 9 element that still 15 feet long by 10 feet wide to move
but then you must use more coax and connector ,and on that kind of system add 10 feet of coax was dramatic ,remember each db of loos ahead of first "gain" stage
directly add itself to noise figure ,so if you use 4 antenna whit 4 x 10" feet of coax you may easy add extra 0.5db of noise figure
here as exemple i have pre-amp and power amp mounted on the foot a less that 10 feet of antenna for minimize coax loss
that you need to manage noise pick-up and dynamic range of the first gain stage those nice preamp start to saturate whit -50dbm signal , then go out of linear zone
and start to ack like mixer ,just lime m 102,1FM radio station example ,and if put filter in front on pre-amp you again loos another 0.5 to 1db of noise figure
and above total 0.5db noise figure your out of the game ,so it quickly start to be real engineering problem |O
but as said on my first post whatever antenna and system you have if your in center of urban zone ,your probably screw-up even before start whit in-band noise
have fun
-
The ambient noise thing is a very valid point, and it's getting worse and worse. I had a Linksys router once situated about 15' from my antenna. It added 10dB to my noise floor on 2m.
This was why I mentioned about slightly under illuminating dishes. Even then, you need to choose a feed that has minimal sidelobes.
Yagis tend to have lobes all over the place, so although the headline gain figure might look great, the side lobes and front to back ratio are all important when considering weak signal stuff. If you have a 15dBi gain Yagi with a nasty 10dB front to back ratio, it means it actually has gain of 5dBi out the back of it, right onto a nice warm noisy Earth.
-
Hi
not to forgot that a very clean Yagis at frequency of intereset may have undesired lode to the interference frequency or event look like omnidirectional :rant:
as noise here in my basement electronic balast fluorescent lamp generate 10 db noise 50 feet away , i may turn my off ,but not one in neibourhood :-//
-
It's starting to look like to be an EME'er you need not only technical prowess, but a pretty decent budget, AND some acres of land.
The good news is the first of those can make up for the second and third :-DMM Just ask Joe Taylor! That was the whole point of his super-slow coded modes (WSJT, JT65), no?
This comparison may be enlightening (Eb/N0 of various amateur-radio modulation types):
http://wwwhome.ewi.utwente.nl/~ptdeboer/ham/tn/tn09b.html (http://wwwhome.ewi.utwente.nl/~ptdeboer/ham/tn/tn09b.html)
I'm not sure what you mean by being able to "hear" an echo. Do you insist on a signal that your brain can detect through your own ears? Many would say the challenge of exchanging a handful of bits, with smaller antennas and lower power, is just as engaging, or more so, even though you can't "hear" anything in the traditional sense.
I will grant you, these digital modes involve long transmissions, so you can't send yourself a signal, and the experience may be slightly less visceral than hearing your own voice echoing back at you...
-
Hi
digital not make magic ,cannot decode signal that not here , if you not "see" it into a spectrogram it will not decode
when said that jt65 decode up to -21db it compare it to same bandwidth of analog signal so ~300HZ wide
but if you use spectrogram (FFT) whit sub HZ resolution , you got same "gain" since noise level was direct relation to it bandwidth
so in real live you will see signal on radio band-scope before software was able to decode it ,assuming you have a decent radio
that good exemple here https://www.youtube.com/watch?v=b63wWmX1mEE (https://www.youtube.com/watch?v=b63wWmX1mEE)
-
It's starting to look like to be an EME'er you need not only technical prowess, but a pretty decent budget, AND some acres of land.
The good news is the first of those can make up for the second and third :-DMM Just ask Joe Taylor! That was the whole point of his super-slow coded modes (WSJT, JT65), no?
This comparison may be enlightening (Eb/N0 of various amateur-radio modulation types):
http://wwwhome.ewi.utwente.nl/~ptdeboer/ham/tn/tn09b.html (http://wwwhome.ewi.utwente.nl/~ptdeboer/ham/tn/tn09b.html)
I'm not sure what you mean by being able to "hear" an echo. Do you insist on a signal that your brain can detect through your own ears? Many would say the challenge of exchanging a handful of bits, with smaller antennas and lower power, is just as engaging, or more so, even though you can't "hear" anything in the traditional sense.
I will grant you, these digital modes involve long transmissions, so you can't send yourself a signal, and the experience may be slightly less visceral than hearing your own voice echoing back at you...
Just to clarify, I don't need to hear a voice come back - although that would be cool.
It seemed in the link I posted earlier ( http://www.vk3um.com/1296_CW_Feb06.wav (http://www.vk3um.com/1296_CW_Feb06.wav) ) that it is possible to hear Morse Code or tones but regardless of the form of the signal (voice, Morse Code, other tones or text, bits, or something else rendered on a display) my first choice would be to receive my own signal as opposed to relying on someone somewhere in the world hopefully receiving it and hopefully reporting it (via "QSO"). I'm not against QSO - it's a great arrangement, but for this project my first choice would be a system that can send a signal and receive that same signal.
Unless I'm missing something, it is possible for an EME system to send and receive a signal (ie, the system can listen for it's own echo), as opposed to, for example, someone in Chicago transmitting a signal to the Moon and someone in Paris receiving the signal and then informing the person in Chicago via QSO that the signal was received in Paris. I'd prefer Chicago-Moon-Chicago vs. Chicago-Moon-Paris-Chicago (or Chicago-Moon-Paris-Moon-Chicago). My impression so far is that Chicago-Moon-Chicago will take a bigger antenna than Chicago-Moon-Paris QSO to Chicago, if any of that makes sense. :) Thanks
-
Hi EME signsal loss was arond +/- 250db so not really care of the distense of both station on earth big part of the loss was moon that it reflex only 7% of signal
but that will affect polarization ,and both eed to see moon in good condition ,that quickly become complex
lunar cycle was 28 day and usually QSO was make a moon rise and set both end ,reason was that wen moon was low on horizon
you got extra ground gain (up to 6db) ,usually we use software for schedule date when it better for contact
since that quicly become complex ,full moon = sun noise over signal ,then moon need to no be over a galaxy or else that emit thermal noise
moon need to be close to heart for gain extra 3db gain ,finally have mood set or rise both end of contact
sure that hear your own echo ,remove from equation polarization shift (still have some liberation fading ) and permit to use ground gain as you need
so usually you have 4-5 very good day by cycle ,but not sure it was good day for other end to and was a convivial time shedule
in really not jsut need the equipment need lot of lerning and $$$$ and most of all time to sped listening noise ;-)
-
Unless I'm missing something, it is possible for an EME system to send and receive a signal (ie, the system can listen for it's own echo), as opposed to, for example, someone in Chicago transmitting a signal to the Moon and someone in Paris receiving the signal and then informing the person in Chicago via QSO that the signal was received in Paris. I'd prefer Chicago-Moon-Chicago vs. Chicago-Moon-Paris-Chicago (or Chicago-Moon-Paris-Moon-Chicago). My impression so far is that Chicago-Moon-Chicago will take a bigger antenna than Chicago-Moon-Paris QSO to Chicago, if any of that makes sense. :) Thanks
Yes, the speed-of-light constraint means that you will need more link margin for an echo to yourself, vs communication with another station. The relative distances are irrelevant, of course. But the maximum duration of the transmission is fixed at the round-trip-time (minus any Tx/Rx switching overhead). This in turn sets an upper limit on Eb (energy per bit) for a given antenna pair, transmit power, and receiver noise floor. Whereas if you were talking to someone else, you could transmit much longer and achieve a much higher Eb.
In practice it is worse than that, because the purpose-designed modes like JT65 require a long transmission (one minute I believe). Thus, getting your own echo back not only places a theoretical limit on Eb but also soaks you with a big penalty for giving up the coding gain of the more sophisticated modulation types.
Of course, it would still be really cool to hear your own voice echoing off the moon ;D
-
Hi EME signsal loss was arond +/- 250db so not really care of the distense of both station on earth big part of the loss was moon that it reflex only 7% of signal
but that will affect polarization ,and both eed to see moon in good condition ,that quickly become complex
lunar cycle was 28 day and usually QSO was make a moon rise and set both end ,reason was that wen moon was low on horizon
you got extra ground gain (up to 6db) ,usually we use software for schedule date when it better for contact
since that quicly become complex ,full moon = sun noise over signal ,then moon need to no be over a galaxy or else that emit thermal noise
moon need to be close to heart for gain extra 3db gain ,finally have mood set or rise both end of contact
sure that hear your own echo ,remove from equation polarization shift (still have some liberation fading ) and permit to use ground gain as you need
so usually you have 4-5 very good day by cycle ,but not sure it was good day for other end to and was a convivial time shedule
in really not jsut need the equipment need lot of lerning and $$$$ and most of all time to sped listening noise ;-)
Ok, so in addition to needing 1) technical prowess, 2) a pretty decent budget, AND 3) some acres of land, we ALSO need 4) enough time to spend listening to noise ;-)
Seriously, I understand this project will require a LOT of learning and a fair amount of time, but the scope of the ambition (one regular human being along with tremendously helpful guidance from fellow EEVers sending a signal to the Moon and receiving it back intelligibly) is what has me spending the cycles to determine if it is feasible. Plus it's fun. In all seriousness, it would be a meaningful accomplishment. I don't generally think in terms of "bucket lists" but if I did, the ability to figure out, deploy, and successfully operate an EME system would be worthy of going on the list.
In any event, I'm slightly hung up on wanting to "hear" (receive) the signal I transmit as opposed to relying on someone somewhere else receiving it and reporting it. I might have to relax this objective - I'm still trying to figure out the impact on the antenna size which so far is the biggest constraint. If the neighbors tell my family we have to move because they don't like my antenna my wife and kids will not be happy campers.
I understand (or I'm learning about) the Faraday rotation and the need/desire for both vertical and horizontal polarization via Polarity Diverse Switching. It seems like this dictates at least two Yagis. Alternatively, it seems like one Yagi with horizontal polarization could work (and could potentially benefit from the ground grain) - which might just mean waiting longer for good days and times and maybe spending more time listening to noise. Based on what I've read so far it seems that one Yagi is a simpler design and avoids some of the potential cabling losses that occur with multiple antennas.
So, given my constraints, let's assume we used one Yagi (horizontally polarized to harness the ground effect). Does this mean that if we are patient about what days and times the system is operated that it would be possible to transmit a short duration signal (maybe 2 seconds of Morse Code) and receive it on the same system? (I'm really hoping the answer is "yes".)
I've waited a long time to bounce a signal off the moon, if I need to make a reservation for certain days and times to avoid galactic noise, no problem. :-+
-
Unless I'm missing something, it is possible for an EME system to send and receive a signal (ie, the system can listen for it's own echo), as opposed to, for example, someone in Chicago transmitting a signal to the Moon and someone in Paris receiving the signal and then informing the person in Chicago via QSO that the signal was received in Paris. I'd prefer Chicago-Moon-Chicago vs. Chicago-Moon-Paris-Chicago (or Chicago-Moon-Paris-Moon-Chicago). My impression so far is that Chicago-Moon-Chicago will take a bigger antenna than Chicago-Moon-Paris QSO to Chicago, if any of that makes sense. :) Thanks
Yes, the speed-of-light constraint means that you will need more link margin for an echo to yourself, vs communication with another station. The relative distances are irrelevant, of course. But the maximum duration of the transmission is fixed at the round-trip-time (minus any Tx/Rx switching overhead). This in turn sets an upper limit on Eb (energy per bit) for a given antenna pair, transmit power, and receiver noise floor. Whereas if you were talking to someone else, you could transmit much longer and achieve a much higher Eb.
In practice it is worse than that, because the purpose-designed modes like JT65 require a long transmission (one minute I believe). Thus, getting your own echo back not only places a theoretical limit on Eb but also soaks you with a big penalty for giving up the coding gain of the more sophisticated modulation types.
Of course, it would still be really cool to hear your own voice echoing off the moon ;D
mark03 - that was a great set of info! It helps clarify a lot! Thanks!!
I get that the transmission duration is bounded (to approximately 2 seconds). What I hadn't yet factored in is that a longer transmission would achieve a (much) higher Eb. (Roughly, what's the penalty for 2 seconds vs 1 minute?)
Additionally, I completely missed on the notion that JT65 type transmission techniques require a somewhat long transmission. I guess in order to sort out what's signal and what's noise JT65 needs more information? I fully believe that a huge part of the link budget's potential efficiency gain comes from the modulation's coding gain.
So, does this mean with 1 Yagi and 2 second transmissions (and the resulting weakened JT65) that Chicago-Moon-Chicago (up and down with a single EME system) is not happening? :(
-
Hi
the 1 minute sequence was since it repeat information lot of time so it heavy FCC error correction
but you may send only a un-modulated carrier for 1 second then stop and hear it back wsjt software handle it in echo test mode
remember that whit bit rate increase you also increase bandwhit and the noise ,so that wly EME communication was so slow
if you what to test a receive station tune it to 143.05Mhz that the french radar grave ,if you not hear it you not be able to listen Ham station
-
Hi
the 1 minute sequence was since it repeat information lot of time so it heavy FCC error correction
but you may send only a un-modulated carrier for 1 second then stop and hear it back wsjt software handle it in echo test mode
remember that whit bit rate increase you also increase bandwhit and the noise ,so that wly EME communication was so slow
if you what to test a receive station tune it to 143.05Mhz that the french radar grave ,if you not hear it you not be able to listen Ham station
OK, 1 minute helps the FEC, roger that
But with a 1 second transmission WSJT will use "echo mode?" This negates the need for the FEC?
So, a 1 Yagi antenna with a 1 second transmission using WSJT in echo mode will enable a signal to be transmitted and then received by the same EME station?
I feel like a ping pong ball :palm:
-
I don't actually have the numbers to tell you what you can hear with a given antenna and TX power, transmitting two seconds of carrier and then listening. With some research you should be able to work out the whole link budget and see. (I have never operated EME.) In principle you can keep reducing your receive bandwidth until the SNR is high enough to see the signal... which is what I think Alphatronique was suggesting with spectrogram software. But remember that a two-second carrier is still not a continuous carrier, and thus it still has finite bandwidth.
To answer (or evade answering) your other questions re: coding and energy per bit... it's complicated. In principle you can increase Eb without limit by transmitting longer symbols, subject only to your patience for a 0.000001 bps throughput :) For some channels, e.g. VLF, you really can go almost as slow as you like (e.g. this transatlantic 8-kHz signal detection using ~ 150 microwatts effective radiated power: http://w4dex.com/vlf/8971Hz/ (http://w4dex.com/vlf/8971Hz/)). Most of the time, though, you end up being limited by the channel's phase coherence. I think I read the EME channel has a coherence time of a few seconds (you should verify this), which would mean longer transmitted symbols have no advantage. So you transmit a series of symbols of that length and use sophisticated error-correction coding, which is what JT65 is doing.
My suggestion is, make a modest investment that will give you plenty of opportunity to play around and get hooked on this stuff first. Then you will have a much better feel for next steps.
-
To get started I would choose 144 MHz... the antennas are not that big and cable losses are fairly low, plus the stuff you buy are fairly cheap.
Now, EME usually means there are two stations involved... i.e. the bigger set up on one side means you can reduce it on the other side. It all comes down to path loss. When they run this w/o computer a basic station for 144 MHz (2meter) would be 1kW output power and 20 dB antenna gain. This would allow you to hear your own echos off the moon. Now some do have a "Slightly Large Array" which means you can hear them off the moon using just a single yagi with 13 dB gain and hear the signal in your receiver. Contacting W5UN should be a walk in the park, and have a look at his antenna: http://www.w5un.net/EME%20Array.JPG (http://www.w5un.net/EME%20Array.JPG)
Contacting KP4AO Arecibo station should be even easier: https://www.youtube.com/watch?v=AIim4VBzi1c (https://www.youtube.com/watch?v=AIim4VBzi1c)
Using JT65 means you have some excotic coding and sophisticated processing to pick up the signal, and allows for very weak signals to be decoded. Ultimately this allows you to down size the station, 14-16 dB antenna gain, and 200 watt o/p may give you 2-way contact.
BTW I have heard the big guns calling on CW using a single yagi and a normal receiver with-out a LNA... guess I was a bit lucky.
Making a random 2-way contact over the moon, now its getting a bit more complicated :D
-
Contacting W5UN should be a walk in the park, and have a look at his antenna: http://www.w5un.net/EME%20Array.JPG (http://www.w5un.net/EME%20Array.JPG)
Nity concept with roling whole construction along ring path ucing classic aka vehicle wheels :-+
The same way decent side dish can be rotated around vertical axis... with all equipment, but longer distance might be needed between front and rare wheels, since dish can have significant stronger air drag, but in the case of strong winds it can move automaticaly with wind direction itself and all we have to do is protect center of this circle to prevent damage, but it can be done quite cheap with decent amount of concrete, so not such a big deal :popcorn:
-
I get that if one station has a relatively bigger antenna the other station can have a smaller antenna.
I'm still keen to figure out what the smallest antenna is that would allow a station to transmit and receive it's own signal (maybe just a couple seconds long) via the Moon. I'm happy to use JT65 or whatever coding technique will minimize the RF requirements, especially the antenna size.
Guess I need to start building a link budget with specifics. If anyone has a preferred link budget calculator that might be suitable for looking at EME system tradeoffs, please post any info or links you have or see. Thx
-
I'm still keen to figure out what the smallest antenna is that would allow a station to transmit and receive it's own signal (maybe just a couple seconds long) via the Moon. I'm happy to use JT65 or whatever coding technique will minimize the RF requirements, especially the antenna size.
Note that a JT65 transmission is 46.8 seconds long, so you're not going to hear the entire transmission echo off the moon. It's a highly structured protocol. Part of the reason the transmissions are somewhat long is to be able to pull signals out of the noise. A detailed explanation is here:
http://www.arrl.org/files/file/18JT65.pdf (http://www.arrl.org/files/file/18JT65.pdf)
Also notice from that paper that a JT65 exchange with another station is essentially self-documenting, and the audio .wav files are saved. Some operators may trade their .wav files via e-mail as a form of QSL after the QSO. It's not quite the same thing as hearing your own voice echo off the moon a couple of seconds after you speak, but it is a form of hearing your own transmission, as received by another station, after it made the round trip to the moon.
Anyway, JT65 is a way to make EME contacts with more modest equipment than would be required for voice or CW.
-
I'm still keen to figure out what the smallest antenna is that would allow a station to transmit and receive it's own signal (maybe just a couple seconds long) via the Moon. I'm happy to use JT65 or whatever coding technique will minimize the RF requirements, especially the antenna size.
Note that a JT65 transmission is 46.8 seconds long, so you're not going to hear the entire transmission echo off the moon. It's a highly structured protocol. Part of the reason the transmissions are somewhat long is to be able to pull signals out of the noise. A detailed explanation is here:
http://www.arrl.org/files/file/18JT65.pdf (http://www.arrl.org/files/file/18JT65.pdf)
Also notice from that paper that a JT65 exchange with another station is essentially self-documenting, and the audio .wav files are saved. Some operators may trade their .wav files via e-mail as a form of QSL after the QSO. It's not quite the same thing as hearing your own voice echo off the moon a couple of seconds after you speak, but it is a form of hearing your own transmission, as received by another station, after it made the round trip to the moon.
Anyway, JT65 is a way to make EME contacts with more modest equipment than would be required for voice or CW.
Thanks for the link - I'll read it but..... Question: JT65 requires at least 46.8 seconds to be fully effective or it requires at least 46.8 seconds to work period? (Can JT65 add value for shorter transmissions, such as 2 seconds?)
-
Thanks for the link - I'll read it but..... Question: JT65 requires at least 46.8 seconds to be fully effective or it requires at least 46.8 seconds to work period? (Can JT65 add value for shorter transmissions, such as 2 seconds?)
The minimum, maximum, and only length of a JT65 transmission is 46.8 seconds. An exchange (QSO) via JT65 involves several back-and-forth 46.8 second transmissions by the two stations involved. You can't just send a couple seconds of JT65.
-
Guess I need to start building a link budget with specifics. If anyone has a preferred link budget calculator that might be suitable for looking at EME system tradeoffs, please post any info or links you have or see. Thx
The best link budget calculator is from Doug VK3UM here...
http://www.vk3um.com/eme%20calculator.html (http://www.vk3um.com/eme%20calculator.html)
This screen shot enclosed is from a recent experiment where NASA were lighting up the moon with their ranging RADAR and some of us in Australia were trying to receive it.
As you can see you can calculate everything that might effect your link budget.
regards
Tim
-
Thanks for the link - I'll read it but..... Question: JT65 requires at least 46.8 seconds to be fully effective or it requires at least 46.8 seconds to work period? (Can JT65 add value for shorter transmissions, such as 2 seconds?)
The minimum, maximum, and only length of a JT65 transmission is 46.8 seconds. An exchange (QSO) via JT65 involves several back-and-forth 46.8 second transmissions by the two stations involved. You can't just send a couple seconds of JT65.
Roger that, Thanks
-
Guess I need to start building a link budget with specifics. If anyone has a preferred link budget calculator that might be suitable for looking at EME system tradeoffs, please post any info or links you have or see. Thx
The best link budget calculator is from Doug VK3UM here...
http://www.vk3um.com/eme%20calculator.html (http://www.vk3um.com/eme%20calculator.html)
This screen shot enclosed is from a recent experiment where NASA were lighting up the moon with their ranging RADAR and some of us in Australia were trying to receive it.
As you can see you can calculate everything that might effect your link budget.
regards
Tim
Wow, on a scale of 1 to 10 this looks like about a 12 :-+ ; after looking at it further maybe a 15
- I'm used to seeing link budget calculators in spreadsheets, and I've never seen a link budget with Planet Path loss and Delay, or a Background Sky Temperature Map, not to mention the integrated antenna database.... This think must have been a labor of love.
I've got the home tab all filled in - the rest looks like it will cause a fair amount of research and learning :-+ :-+
Thanks!
-
a little off topic but looks like Beethoven has been to the Moon
http://www.katiepaterson.org/eme/ (http://www.katiepaterson.org/eme/)
-
Ok, an update on my quest to figure out what the smallest direct up and down EME system configuration might be.
I was hoping a single yagi might possibly do it but I think the answer is "not even close", ie, 4 yagis appear unlikely to get the job done, and probably something in the vicinity of 8-16 yagis would be required - which would freak out my neighbors, I'm sure.
I came across some very good posts by VE2ZAZ.
System Overview (excellent video)
https://www.youtube.com/watch?v=GECJx_wHpoc (https://www.youtube.com/watch?v=GECJx_wHpoc)
Project Log
http://ve2zaz.net/EME_Log/EME_Log.htm (http://ve2zaz.net/EME_Log/EME_Log.htm)
Project Overview
http://ve2zaz.net/3.2m_Dish/3.2m_Dish.htm (http://ve2zaz.net/3.2m_Dish/3.2m_Dish.htm)
VE2ZAZ's take is this:
A single yagi will always be very borderline, no matter what you do or how much power you put into it. A single long boom yagi will have you going on digital modes with the largest stations, but it will not really cut it on CW. Even 4 yagis like mine are a small setup. Do not expect to hear (or see) yourself with 4 yagis. 8 or 16 yagis will make this happen, but this is a large array! This is why I went to 1296 and a 3.2m dish on the ground. With 100W at the feed, I could see and hear myself under good moon conditions. But I never saw my own signal on 432 with my four 13-element yagis and 300W. My four yagis allowed to work CW with larger stations and JT65 with many.
A very low noise preamplifier right at the antenna will always be the single most important thing to have (except on 6m, where to level of ambient noise is high).
But you will not be able to really compensate for too small antenna(s). On TX, you can go KiloWatt, but that will not improve your RX. Even the best preamp will not help if there is too little energy picked up by the antenna...
So, assuming you want to work/with other stations it looks like the entry level for EME can be a single Yagi similar to what K4MSG built:
http://www.k4lrg.org/Projects/K4MSG_EME/ (http://www.k4lrg.org/Projects/K4MSG_EME/)
But to go straight up and down (to hear or see your own signal without relying on other stations) requires more antenna resource, something along the lines of what VE2ZAZ built.
PS, I'm not saying all this is 100% iron clad and there aren't other answers, configurations, and solutions - but I think K4MSG and VE2ZAZ have pushed hard on what can be done with physics, technology, budget, and ingenuity and so far these are the best data points I've found. Happy to hear other ideas.
-
It all comes down to tradeoffs. At 144MHz, path loss is a tad more than 250dB typically; at 432 the loss is more like 260dB, and at 1296MHz it is more like 270dB. So, you need more antenna gain (and power) as you move up in frequency. The good thing is that antennas are proportionally smaller as the frequency goes up for a given amount of gain, so it's "easier" to have higher gain antennas in a given physical space when operating at the higher frequencies.
Here are some references that I got from a colleague - some of which have probably been referenced earlier in the thread:
http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf (http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf)
http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf (http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf)
http://pa3csg.hoeplakee.nl/joomla25/images/stories/PDF/eimac/AS-49-8.pdf (http://pa3csg.hoeplakee.nl/joomla25/images/stories/PDF/eimac/AS-49-8.pdf)
http://www.qsl.net/n1bwt/chap6-2.pdf (http://www.qsl.net/n1bwt/chap6-2.pdf)
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969AJ.....74.1214H&defaultprint=YES&page_ind=3&filetype=.pdf (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969AJ.....74.1214H&defaultprint=YES&page_ind=3&filetype=.pdf)
-
I'm not a HAM but a while back I looked at crystal filters ... and I found this hear say account (http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/radcom/1994/09/page55b/index.html) of someone doing it with 4 Yagi's and 500 Watt (with a 20 Hz bandwidth).
-
It all comes down to tradeoffs. At 144MHz, path loss is a tad more than 250dB typically; at 432 the loss is more like 260dB, and at 1296MHz it is more like 270dB. So, you need more antenna gain (and power) as you move up in frequency. The good thing is that antennas are proportionally smaller as the frequency goes up for a given amount of gain, so it's "easier" to have higher gain antennas in a given physical space when operating at the higher frequencies.
Here are some references that I got from a colleague - some of which have probably been referenced earlier in the thread:
http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf (http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf)
http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf (http://physics.princeton.edu/pulsar/K1JT/EME_2010_Hbk.pdf)
http://pa3csg.hoeplakee.nl/joomla25/images/stories/PDF/eimac/AS-49-8.pdf (http://pa3csg.hoeplakee.nl/joomla25/images/stories/PDF/eimac/AS-49-8.pdf)
http://www.qsl.net/n1bwt/chap6-2.pdf (http://www.qsl.net/n1bwt/chap6-2.pdf)
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969AJ.....74.1214H&defaultprint=YES&page_ind=3&filetype=.pdf (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1969AJ.....74.1214H&defaultprint=YES&page_ind=3&filetype=.pdf)
Thanks. The challenge with going up in frequency is that while it brings shorter wavelengths and therefore potentially a smaller antenna is that the electronics and ancillary equipment are likely to go up in price, I think - but it's worth looking into.
One thing I'm pretty sure of is that if the antenna is big enough to stand on it probably isn't going to fly with the neighborhood/HOA expectations :)
-
I'm not a HAM but a while back I looked at crystal filters ... and I found this hear say account (http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/radcom/1994/09/page55b/index.html) of someone doing it with 4 Yagi's and 500 Watt (with a 20 Hz bandwidth).
Thanks, this is a cool article and it does seem to indicate that with 4 yagis the system described goes "up and down" without a need to go "across" for help from another station. This is why I put my disclaimer about my findings not being 100% iron clad. It's not too hard to envision something that sits in the gaps between these first couple benchmark systems (excellent as they are), but even at 4 yagis unfortunately it doesn't address the original objective which is to get the size down to 1 manageable yagi (that could be somewhat temporary/portable) in an effort to meet the neighborhood aesthetics constraint. This project is making the suburbs look disadvantageous to rural settings.... And I'm sure people in rural settings could come up with some other good reasons to live farther from cities beyond just the ability to do some Moonbouncing :)
-
A different Idea
For receive,
have you looked at combining an active antenna with a traveling wave amplifier.
The electronics of an active antenna allows a large range of input impedance so you could have many taps on one dipole. There would be a signal time difference between taps.
The traveling wave amplifier or Distributed amplifier uses a time difference to build the signal.
http://en.wikipedia.org/wiki/Distributed_amplifier (http://en.wikipedia.org/wiki/Distributed_amplifier)
Add in the active antenna preamp in where the gates are in the figure or use dual gate transistors.
You could also use a Distributed amplifier to add many dipoles.
In place of the many dipoles, I think it would work with a long wire( a pipe ).
Will it work, No idea
C
-
Path loss is also proportional to the square of the frequency, so it's swings and roundabouts.
Think of it more in terms of antenna aperture size. The more metal you have in the air, irrespective of frequency, the louder the signal will be.
Higher frequencies means it's also harder to accurately align your antenna because the beamwidth is narrower for the same antenna area. Receiver noise figures also tend to increase as you go up in frequency, although these days even at 10GHz you can achieve sub 0.5dB noise figures reasonably easily.
I remember trying to pick up a satellite in near Molniya orbit about 15 years ago on K band with a 60cm dish, giving about a 1.5 degree beamwidth. Picking it up and tracking by hand was very hard!
-
Path loss is also proportional to the square of the frequency, so it's swings and roundabouts.
Think of it more in terms of antenna aperture size. The more metal you have in the air, irrespective of frequency, the louder the signal will be.
Roger that, my problem/challenge is that once something starts to look like more than a DirecTV dish (about 1 meter or less) or like a regular old-fashioned (yagi) TV antenna it won't pass the aesthetic judgment. In fact, of the two, a 1 meter dish might be easier to camouflage than the yagi. If it weren't for the appearance constraint the idea of a 3 meter dish seems like a winner - works at a reasonable frequency, not too hard to point, works with a reasonable amplifier and receiver. I think the answer is live without straight up and down or find another place to implement the system, or find another project :(, but I'm not there yet...
-
One thing I'm pretty sure of is that if the antenna is big enough to stand on it probably isn't going to fly with the neighborhood/HOA expectations :)
Well even before EME and HOA expectations, some wise Ham once coined the phrase "If your antenna didn't fall down last winter then it's too small." ;)
-
One thing I'm pretty sure of is that if the antenna is big enough to stand on it probably isn't going to fly with the neighborhood/HOA expectations :)
Well even before EME and HOA expectations, some wise Ham once coined the phrase "If your antenna didn't fall down last winter then it's too small." ;)
That is a good one :-DD :-+
Sometimes empirical evidence can lead the way even ahead of math.
If anyone interested in EME link budgets (or link budgets in general) hasn't take the opportunity to download vk3um's EME Calculator you might want to check it out - it is an impressive program.
http://www.vk3um.com/eme%20calculator.html (http://www.vk3um.com/eme%20calculator.html)
But someone may have to contact vk3um to let him know that he needs to add another tab that accounts for this ("If your antenna didn't fall down last winter then it's too small.") variable. :)
-
Horn..
A horn made out of chicken wire or even a discarded cardboard refrigerator box or foam core covered with aluminum foil would have enough gain. You could fold it up when you weren't using it.
Seriously. The first radio telescope was a horn. Balance it on its center of gravity so you can steer it by hand..then sit out on your lawn with a deck chair and wait for the moon to rise.. It might be funny looking but it would get the job done.
-
Most horn configured antennas are typically used to irradiate the dish as their gain is too low i.e. they are too broad an angle often 30degrees. The dish is just a reflective structure not the real 'antenna'. Horns also allow relatively easily rotary polarisation (helps with Faraday rotation effect) but also typically include the ability to have reverse polarity on receive as compared with transmission.
Currently on of the better designs appears VE4MA Super, the recent publication of DUBUS Vol 44 2/4 (the German radio Society's VHF technical publication) has an excellent article by Paul Wade W1GHZ (he also has an excellent website like VK3UM) on gain/temp noise of the various commonly used feed horns.
EF if you get it up and going I might be there as well, currently I have about 300W at 1296MHZ PA going OK, some PSU and computer interface issues at present.
-
Most horn configured antennas are typically used to irradiate the dish as their gain is too low i.e. they are too broad an angle often 30degrees. The dish is just a reflective structure not the real 'antenna'. Horns also allow relatively easily rotary polarisation (helps with Faraday rotation effect) but also typically include the ability to have reverse polarity on receive as compared with transmission.
Currently on of the better designs appears VE4MA Super, the recent publication of DUBUS Vol 44 2/4 (the German radio Society's VHF technical publication) has an excellent article by Paul Wade W1GHZ (he also has an excellent website like VK3UM) on gain/temp noise of the various commonly used feed horns.
EF if you get it up and going I might be there as well, currently I have about 300W at 1296MHZ PA going OK, some PSU and computer interface issues at present.
VK5RC,
Looks like your design has some similarities to VE2ZAZ in terms of dish size and operating at 1296 MHz. Any other similarities or differences between his design and yours that you see as notable? At the time you posted the other day I was pretty focused on a yagi antenna but now that it seems like the conclusion is that 1 yagi isn't going to go straight up and down I guess I have to consider a parabolic antenna. It looks like you have done a nice job of making it movable - but I can't tell from your photo where you might be moving it to? Does it fit through your garage doors and live in the garage when not in operation? Thx, EF
-
Hi EF,
Unfortunately it does not fit through the garage doors, it is about 3.8m tall, when the dish is vertical. I store it around the side of the house and to do so must remove the coax, feed horn, the feed horn support (actually a bit of bent motor car exhaust pipe) and the extension pieces for the front legs of the Engine mount/dish support. It takes about 10-15 mins to set it up and another 15 to take down. It has to go through a 1.3m wide gait and stores down the side of the house, chained to the house wall for wind issues. I have only fired it up a couple of times as it does take a bit of organising with my work and the moon needs to be in a position where I can see it (to aim the dish)The moon can't be too close to the sun and I don't really want to be doing this at 3am local time.
One of the more useful exercises was to look for sun noise, this involved experimentally confirming that the focal point of the dish was where it should be and the equivalent of the feed horn similarly. 2cm off can be 3dB difference. It also allows you to know if the dish has a 'squint' i.e. does it look electrically where it is pointed physically. I built a 3 pole 1296MHz band pass filter and used a USB dongle radio, the FunCube Pro2+ and Spectrum lab to average the noise. I am a few dB down on what it should be (cold sky to sun noise)according to VK3UM calculator. I have taken about 18months to get where I am but am not in a great rush as then I will have to think of something else! Actually thinking of looking at some ionosphere RF pulse responses, using the dish and power amps etc.
Below is the dish stored. Note it is a 3m dish not 4m as photo labelled.
Remember the fun is the process of getting there! I have learnt a lot along the way.
-
Hi EF,
Unfortunately it does not fit through the garage doors, it is about 3.8m tall, when the dish is vertical. I store it around the side of the house and to do so must remove the coax, feed horn, the feed horn support (actually a bit of bent motor car exhaust pipe) and the extension pieces for the front legs of the Engine mount/dish support. It takes about 10-15 mins to set it up and another 15 to take down. It has to go through a 1.3m wide gait and stores down the side of the house, chained to the house wall for wind issues. I have only fired it up a couple of times as it does take a bit of organising with my work and the moon needs to be in a position where I can see it (to aim the dish)The moon can't be too close to the sun and I don't really want to be doing this at 3am local time.
One of the more useful exercises was to look for sun noise, this involved experimentally confirming that the focal point of the dish was where it should be and the equivalent of the feed horn similarly. 2cm off can be 3dB difference. It also allows you to know if the dish has a 'squint' i.e. does it look electrically where it is pointed physically. I built a 3 pole 1296MHz band pass filter and used a USB dongle radio, the FunCube Pro2+ and Spectrum lab to average the noise. I am a few dB down on what it should be (cold sky to sun noise)according to VK3UM calculator. I have taken about 18months to get where I am but am not in a great rush as then I will have to think of something else! Actually thinking of looking at some ionosphere RF pulse responses, using the dish and power amps etc.
Below is the dish stored. Note it is a 3m dish not 4m as photo labelled.
Remember the fun is the process of getting there! I have learnt a lot along the way.
I'm with you, it's a journey as much or more than a destination.
I think what you are building is along the lines of something I'd really enjoy attempting and hopefully doing but I'm not sure if I have the skill and knowledge to figure it all out. I have a hunch with time it might be possible and it sure would be a great accomplishment - so I definitely admire what you and others are doing.
You mentioned you are a few dB down; is that extra margin you will have when you find those dBs or do you need to find them to get it fully operational? Have you been able to get a signal up to the Moon and directly back to your station? If so, that is spectacular in my book and even to be on the doorstep is very cool.
As for the storage arrangement I might have to look for an even more modular approach to get it all in the garage when not in operation - the antenna diameter seems to be the gating factor.
-
I still don't see any practical way to build an EME station that would be: a) small enough to not bug the neighbors, b) within my skillset and justifiable budget, and c) go "Up and Down", ie be able to hear/detect it's own signal reflected off the Moon vs. relying on a larger second (third-party) station to report hearing/detecting the signal - but I'm still thinking about it.
Today I came across this video with some good history/background and insight (it's probably more useful for potential new EME'ers than experienced EME'ers):
https://www.youtube.com/watch?v=uIQqZL_3xR0&app=desktop (https://www.youtube.com/watch?v=uIQqZL_3xR0&app=desktop)