Author Topic: RF module hunting  (Read 18908 times)

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Offline aaronhance

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RF module hunting
« on: February 11, 2016, 12:47:01 pm »
I've been spending hours looking at RF modules, but I can't seem to find anything that will suit my needs! I was wondering if anyone knows of any that will. I'm looking for something with 500kbps(preferably 1mbps) data rate with 5mile line of sight range.

This is the closest I've found to what I need: http://www.digi.com/products/xbee-rf-solutions/modules/xtend-module#specifications
The data rate would limit me to sending 1fps low quality encoded footage.
 

Offline Muxr

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Re: RF module hunting
« Reply #1 on: February 11, 2016, 01:02:11 pm »
 

Online PA0PBZ

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Re: RF module hunting
« Reply #2 on: February 11, 2016, 01:44:31 pm »
Never used it, but this advertises to be what you're looking for: (url)

I doubt it: The low data-rate (down to few bytes per second)...
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Offline aaronhance

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Re: RF module hunting
« Reply #3 on: February 11, 2016, 02:19:23 pm »
Could I use an amplifier to boost the signal strength from a module?
 

Offline KD0CAC John

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Re: RF module hunting
« Reply #4 on: February 11, 2016, 02:45:01 pm »
Could I use an amplifier to boost the signal strength from a module?

And what are you going to amplify to , what is the RF transmit rules in your location  ??
 

Offline tggzzz

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Re: RF module hunting
« Reply #5 on: February 11, 2016, 02:49:58 pm »
Could I use an amplifier to boost the signal strength from a module?
Only if you are prepared to risk interfering with other radio users (especially those in different parts of the spectrum), to have a visit from The Authorities, and subsequent criminal proceedings.

If you have to ask why that might be the case, you should go and visit your local ham radio society.

Hint: in general radio transmissions require individuals to have licences which are granted after they have passed exams. There are exceptions for certain classes of well-tested equipment, but a transmitter such as you are proposing would definitely not qualify for an exemption: it would be illegal for very good reasons. BTW, it is prefectly legal to sell equipment that it is illegal to operate.
« Last Edit: February 11, 2016, 02:51:31 pm by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline han

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Re: RF module hunting
« Reply #6 on: February 11, 2016, 03:20:49 pm »
You could use long range WIFI repeater, so no HAM license needed, and its already working..
example https://www.ubnt.com/products/
 

Offline aaronhance

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Re: RF module hunting
« Reply #7 on: February 11, 2016, 03:30:15 pm »
You could use long range WIFI repeater, so no HAM license needed, and its already working..
example https://www.ubnt.com/products/

I should have mentioned this is for a UAV, so it needs to be lightweight. Could I have an amazing ground receiver to improve the range?
 

Offline bookaboo

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Re: RF module hunting
« Reply #8 on: February 11, 2016, 05:25:36 pm »
You can do whatever you like on the receiver antenna (as long as you don't transmit on the same antenna).
Might be an idea to send your requirement to LPRS and Radiometrix, both are very helpful technically and as long as you stick to recommended transmitter antennas you won't break any laws or annoy anyone else.
 

Offline tggzzz

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Re: RF module hunting
« Reply #9 on: February 11, 2016, 11:18:49 pm »
You could use long range WIFI repeater, so no HAM license needed, and its already working..
example https://www.ubnt.com/products/

I should have mentioned this is for a UAV, so it needs to be lightweight. Could I have an amazing ground receiver to improve the range?

That wouldn't break any man-made laws, so you only have physics to limit you.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline uncle_bob

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Re: RF module hunting
« Reply #10 on: February 12, 2016, 12:23:43 am »
You could use long range WIFI repeater, so no HAM license needed, and its already working..
example https://www.ubnt.com/products/

I should have mentioned this is for a UAV, so it needs to be lightweight. Could I have an amazing ground receiver to improve the range?

Hi

Ok, so now you have the opportunity to criminally interfere with communications over a large geographic are. Plus you have broken a number of aircraft specific (type acceptance) rules as well. The large area is pretty much guaranteed to attract the sort of attention you do not want .....

Is this really worth going to jail for a few years?

Why is this so? The RF spectrum is packed with users. There are an enormous number of people who would love to use the spectrum, waiting in the wings. The only way to prevent chaos is regulation. Since not everybody likes rules, there is also active enforcement. Some chunks of the spectrum are used by the military. Think in terms of *very* active enforcement if you hit the wrong channel.

Yes, if you are off in a country nobody can find on a map, you can get away with this or that. If your country information is correct, you are in a country that *does* have rules and enforcement.

Bob


 

Offline hendorog

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Re: RF module hunting
« Reply #11 on: February 12, 2016, 09:20:28 am »
I've been spending hours looking at RF modules, but I can't seem to find anything that will suit my needs! I was wondering if anyone knows of any that will. I'm looking for something with 500kbps(preferably 1mbps) data rate with 5mile line of sight range.

This is the closest I've found to what I need: http://www.digi.com/products/xbee-rf-solutions/modules/xtend-module#specifications
The data rate would limit me to sending 1fps low quality encoded footage.

Do you need digital? The norm for FPV is analog which means its cheap and easy.
If you need digital then wifi should work. It's used in that low cost Parrot drone.
2.4GHz is pretty much the standard for RC model control. So you ain't going to jail for using that frequency as there are not enough jails to hold us all :)

By all means check the regs and don't be reckless.
 

Offline tggzzz

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Re: RF module hunting
« Reply #12 on: February 12, 2016, 09:30:17 am »
Is this really worth going to jail for a few years?
If your country information is correct, you are in a country that *does* have rules and enforcement.

Being in the same country, I can confirm that.

When I applied for a licence to transmit on a very low power within a building, the local detection/emforcement people came around before granting the licence. We had a great time together, I applied a suggestion they made, and I got the licence.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline tggzzz

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Re: RF module hunting
« Reply #13 on: February 12, 2016, 09:41:24 am »
2.4GHz is pretty much the standard for RC model control. So you ain't going to jail for using that frequency as there are not enough jails to hold us all :)

You are correct - providing that is the only frequency used, plus provided it is within the legal power limits. If either of those is not the case then expect "A Visitor" to appear unexpectedly. Starting question: if you are using modulation type M on a carrier frequency F with power P through a component with an IP3 of XdBm and saturation at YdBm, what powers at what frequencies would you expect to see being emitted at the antenna. If you think the frequencies will be limited to F+-deltaF, then "bzzzt, go to jail, do not pass go".

I doubt the OP has sufficient knowledge to understand and/or measure let alone constrain the transmitted frequencies.

The OP would be well advised to talk to their local radio hams.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline hendorog

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Re: RF module hunting
« Reply #14 on: February 12, 2016, 10:13:53 am »
2.4GHz is pretty much the standard for RC model control. So you ain't going to jail for using that frequency as there are not enough jails to hold us all :)

You are correct - providing that is the only frequency used, plus provided it is within the legal power limits. If either of those is not the case then expect "A Visitor" to appear unexpectedly. Starting question: if you are using modulation type M on a carrier frequency F with power P through a component with an IP3 of XdBm and saturation at YdBm, what powers at what frequencies would you expect to see being emitted at the antenna. If you think the frequencies will be limited to F+-deltaF, then "bzzzt, go to jail, do not pass go".

I doubt the OP has sufficient knowledge to understand and/or measure let alone constrain the transmitted frequencies.

The OP would be well advised to talk to their local radio hams.

Hams generally know very little about FPV in my experience. It might be different in the UK, but that is certainly the case here. Asking RC clubs might be an option, although they can also be very traditional. No harm in asking but brace yourself for a lecture :)

Yeah I get your point. But if anyone turns up to question you, then you must have done something grossly wrong which is affecting another user. That would be reckless, so the point is don't do that :)

For the OP, it appears the UK regs are here for RC vehicles, and they are limiting.
http://stakeholders.ofcom.org.uk/spectrum/information/licence-exempt-radio-use/licence-exempt-devices/ofw311

100mW eirp at 2.4GHz isn't much, but if you build or buy good antennas it should go a fair old way. 25mW on 5.8 GHz is even less, but that can still go several km's if you know your stuff - according to this old thread.
http://fpvlab.com/forums/showthread.php?2261-5-8-GHz-ranges

 

Offline tggzzz

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Re: RF module hunting
« Reply #15 on: February 12, 2016, 10:55:41 am »
The OP would be well advised to talk to their local radio hams.
Hams generally know very little about FPV in my experience.
They know about radio transmissions, which is the issue here.
Quote
Yeah I get your point. But if anyone turns up to question you, then you must have done something grossly wrong which is affecting another user. That would be reckless, so the point is don't do that :)
They came and talked to me before I started transmitting.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Online Ian.M

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Re: RF module hunting
« Reply #16 on: February 12, 2016, 11:41:45 am »
See: https://www.caa.co.uk/Commercial-industry/Aircraft/Unmanned-aircraft/Small-unmanned-aircraft/ which indicates the main regulatory restrictions that hobby FPV drones fly under in the UK.   
Quote
The aircraft must be kept within the visual line of sight (normally taken to be within 500 m horizontally and 400 ft. vertically) of its remote pilot (i.e. the ‘person in charge’ of it).

That's within the range that a good licence free (IR2030/27/2) omnidirectional 2.4GHz 10mW UAV video sender, with a high gain directional antenna on the receiver is good for.  Either operate as a two man team, one piloting and the other manually tracking the UAV with the receiving antennae (and possibly standing by with a buddybox as the required backup VFR pilot), or design a GPS tracker that calculates the relative bearing and elevation of the UAV from the base station and controls the antenna accordingly.  You can modulate telemetry data e.g. UAV GPS position onto the video sender's audio link (if implemented) or onto a scanline at the top or bottom of the frame to enable this. To avoid the problems of high slew rate tracking close in, a second omnidirectional receiving antenna would be advisable, with auto-switching based ideally on RSSI, but if the modules used don't support that,  on how clean the sync pulses (and audio channel if implemented) are.

« Last Edit: February 12, 2016, 05:52:03 pm by Ian.M »
 

Offline GandalfDerGraue

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Re: RF module hunting
« Reply #17 on: February 12, 2016, 01:03:56 pm »
...
You could use long range WIFI repeater, so no HAM license needed, and its already working..
example https://www.ubnt.com/products/
... and even this is illegal in some countries. Always be sure to check if there is a regulatory for the frequency range you're planning to use, if not or if in doubt better don't use. It has to be positively *allowed* to be used for more or less public usage, all other cases and frequencies are definitely prohibited.  :-//
 

Offline tggzzz

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Re: RF module hunting
« Reply #18 on: February 12, 2016, 03:51:10 pm »
You could use long range WIFI repeater, so no HAM license needed, and its already working..
example https://www.ubnt.com/products/

Not true. WiFi transmitters are legally limited by EIRP, not power.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Online PA0PBZ

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Re: RF module hunting
« Reply #19 on: February 12, 2016, 04:06:12 pm »
Not true. WiFi transmitters are legally limited by EIRP, not power.

Sure, but good luck putting an antenna with some gain on a UAV.
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Offline janoc

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Re: RF module hunting
« Reply #20 on: February 12, 2016, 04:43:44 pm »
I think this debate about frequencies and power and licensing is pretty much a moot point. If the goal is to operate an UAV at (up to) 5 mile range then that certainly breaks the rules about flying within visual range.

Even a spotter buddy next to the pilot won't see squat at such distance unless the OP is intending to fly an UAV the size of a commercial jet. (And how many FPV flyers actually use spotters??)

My advice would be - just don't and find something better to do. This is asking for serious problems, especially with all that "anti-drone" law enforcement attention today thanks to the reckless idiots flying UAVs close to airports, in the way of large manned traffic, over cities, etc.

« Last Edit: February 12, 2016, 04:45:27 pm by janoc »
 

Offline LaserSteve

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Re: RF module hunting
« Reply #21 on: February 12, 2016, 05:33:15 pm »
Keep in mind that nearly all WIFI or " License Free"  ISM frequencies  of 420 Mhz and up are allocated on a PRIMARY basis to RADAR, both Military and Civilian. Wideband sources of such frequencies at any reasonable altitude start showing up when the receive antenna is a four meter wide cosecant squared radar  antenna. 

5.6 Ghz Professional WIFI has became a real problem in some places for  Doppler Weather Radar in the US.  This generally happens when certain firmware settings get changed, but it is a problem.  It is also very close to/overlaps  a marine radar band in 90% of the world.

A short duration, very low power,  narrow pulse, which was the original intent of the "license free" frequencies world wide, was not going to interfere much.  Especially with 2.4 Ghz which is strongly adsorbed by organics and trees leaves. However if you get said source airborne on a high gain antenna, your going to get noticed. The question is, how long will you be ignored if your close in to the Radar.

1.2 Ghz in the United States  is very, very,  close in frequencies  to the long range radars which protect our borders.. Granted they probably  have a anti-jam "waveform" they can use, but if they have to switch to that mode, your going to get a visit.

There are also some severe localized  restrictions on where you can use 420-450 Mhz in the US and UK...

Another big Sin would to be to fly in a "National Radio Quiet Zone" which exist in various places around the world. We have a huge one in the US.
It's monitored for emissions, trust me. Even cellular and FM and AM radio  is banned there with a few exceptions.

So when the white or black SUV pulls up, which can happen, what are you going to say? Said vans usually have a slightly extended  addition to the roof.  These days they hunt you with TDOA or TOF  systems, so the hunting antenna is very small and discrete.

Steve








« Last Edit: February 12, 2016, 05:42:21 pm by LaserSteve »
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Offline aaronhance

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Re: RF module hunting
« Reply #22 on: February 12, 2016, 05:42:00 pm »
 Thanks for the input guys! After reading lots, I'm going to be using 2.4Ghz 100mw transceiver(for video), I will also be looking into building an auto-tracking antenna.

EDIT: Would I be able to use an amp from the receiver antenna?
« Last Edit: February 12, 2016, 05:52:59 pm by aaronhance »
 

Online Ian.M

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Re: RF module hunting
« Reply #23 on: February 12, 2016, 05:56:40 pm »
You may want to take a look at this blog:
http://fpvuk.blogspot.co.uk/2012/12/uk-telemetry-fpv-frequencies.html which summarises the legal systems for FPV in the UK.  100mW @2.4GHz is only legal on a UAV if it uses digital modulation.
« Last Edit: February 12, 2016, 07:15:38 pm by Ian.M »
 

Offline aaronhance

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Re: RF module hunting
« Reply #24 on: February 12, 2016, 07:14:12 pm »
Thanks Ian!

How accurate would you guys say this is?


 


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