Author Topic: Any Shortwave Radio Tips for a Noob Considering the Hobby?  (Read 5809 times)

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Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #25 on: December 08, 2019, 08:14:51 pm »
Just get that cheap Tecsun 310 and use the whip antenna or throw a skinny wire out the window.  This will work well enough to get you some useful hands-on experience while you are reading up on the hobby.  If you end up getting a better radio or get your ham ticket the Tecsun will still be a fun radio to have.  And they work!  For example, I've used a similar (cheap) receiver, with the headphone jack connected to my laptop mic-in jack to pick up and decode NOAA weatherfax signals.  I was in northern California and the transmitter was in Hawaii.
 

Offline Bud

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #26 on: December 08, 2019, 08:17:03 pm »
I hope it's not a hobby going extinct, although I imagine as the folks involve age there is more incentive to keep the young ones interested (and now you compete with many more hobbies that seem to attract young ones) to pick up the torch.
No worries, people still go hunting using flintlock muzzleloaders.
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Offline VK3DRB

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #27 on: December 09, 2019, 07:27:00 am »

But if you have a ham radio you will be able to communicate, assuming your infrastructure is destroyed and you were not vaporised. If this sounds far fetched, look what happened in Cyclone Tracey in 1974 which wiped out an entire city of Darwin. Ham radio was the ONLY form of communication to the outside world for several days. The main link was between a ham with a generator in Darwin and a ham in Melbourne.
 

You don't have to look back that far. I'm pretty sure I heard Ham radio was involved in saving more than a few lives in the aftermath of hurricane Katrina.

In Texas (where I once resided), ham radio license number plates for you car were $1 per year. That was because the State of Texas recognises the technical contribution and potentially the emergency contribution ham radio operators can provide. The plates cost around $500 in Victoria. When I came back to Victoria, I lobbied to get the law changed to allow hams to get low cost number plates and I was effectively told to get lost. Technical people need a lot more recognition in our society.
 

Offline CJay

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #28 on: December 09, 2019, 10:08:49 am »
Thanks again for all the suggestions. I've heard back from a few HAM clubs, I may go to a meeting soon and see what is going on. Meanwhile a few ways I can learn more is read some intro books and I found a page on Ultralight DXing here: http://www.hard-core-dx.com/nordicdx/dxlab/mwdx.html

FWIW, I'd recommend the Tecsun and an SDR dongle, that way you're covered 'from DC-Daylight', neither are a top class performers and you willget fed up of their shortcomings if you advance in the hobby but both are good enough to see if you have a taste for it and both will find a place in a 'better' shack as you progress onto bigger and better things, for instance, the cheap SDR dongles are really useful little tools in a workshop, specturm analyser software, interference tracking etc.

You can throw both in a bag easily if you find yourself going on a business trip, holiday etc. so you can listen wherever and neither is a huge loss if you break or lose them.

Neither will break the bank, yes there are better pieces of gear out there but the price to performance is excellent for those cheap little items, the next step up is more than ten times the price of either (if you buy new) 
 
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Online edy

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #29 on: December 09, 2019, 01:51:57 pm »
Thanks again for all the advice! I ended up biting the bullet and ordered the Tecsun PL-310ET from Amazon. It was roughly ~$43 US or $57 CAN with free shipping. I had about $50 CAN saved up in Amazon gift cards already (for filling out some Developer surveys over the past year) which covered almost all of it. And best of all, it will arrive in 1-2 weeks instead of 2-3 months (like stuff I order from eBay)!  :-DD

Meanwhile I have the following e-books to read through:

  Ham Radio For Dummies 2nd Ed (2013)
  The ARRL Ham Radio License Manual (3rd Ed) - Technician
  The Beginners Handbook of Amateur Radio (4th Ed)
  Basic Amateur Radio Course (EmComm)

So that should get me started and "scratch the itch" with minimal cost invested at this point, to see if I enjoy and want to get into the hobby more. Again, the issue is mostly time. I am already stretched thin with work/family and the wife/kids are not going to enjoy this unless I bring them along with the hobby. So I think this is an easy way to nudge along, do some family listening and exploring and learning.  :-+

Once I have had my fill of the Tecsun, I will probably explore a RTL-SDR dongle. I run Ubuntu Linux so will need to play around with some of the software and get drivers to make it work, plus figuring out how to set up some antennas. I don't have the ability to go crazy with antennas, so I think I will need to find a solution involving some wires that I can string up in the upstairs bedroom temporarily when I am using the radio, or a clip-on wire that I can make myself (I have plenty of 1/8" jacks, wires and metal clips, coax cable, etc). I was tempted to buy one of the Tecsun "retractable wires" that came suggested by Amazon for another $15 but reviews were mixed as to how much better it was over the standard flip-out telescopic antenna already attached to the unit. So before I shell out more money, I will try the existing antenna and if needed I will try to build something out of scrap from home and see if it helps.

Yes I also agree that both the Tecsun and RTL-SDR are cheap enough and fairly portable so I can move them around and play with it on trips, at work, camping, etc.... I looked at some of the cheapest SSB options and they are at least 2-3x the cost of this model. They start around $100-150 CAN and quickly go up in the $200+ range. I also realized that most Ham used equipment is still going to fetch a fairly high price, and anything that is in the lower end is not going to have the convenience of this Tecsun with digital tuning and memory presets. That is the reason I chose the PL-310ET over the R-909, which is less than half the price ($15-20). The tuning on the R-909 will make life harder. At least with a digital display I can save and log signals I find.

I also got the Tecsun manual which I downloaded from here:

https://www.tecsunradios.com.au/store/wp-content/uploads/2015/12/PL-310ET-MANUAL.pdf

It shows the following frequency range:

FM   87~108 MHz
   Russia   64~108MHz
   Japan    76~108 MHz
   EU, USA  87.5~108 MHz
MW     522~1620 kHz
   USA 520~1710 kHz
LW 153~513 kHz
SW 2300~21950 kHz

I am assuming that "FM" specifically looks for FM signals in that range (Frequency modulated mode). Then should I assume that the signals that are interpreted by my Tecsun in the other ranges (MW, LW, SW) are going to be considered all be "AM" type (amplitude modulation) of the carrier wave? I have seen that all kinds of signals can be transmitted at all kinds of frequencies, from digital signals to TV/picture, to AM/FM encoded and more. I guess the radio will hear a bunch of weird noise when I tune into those frequencies if it is not AM? Will plugging the output into my computer and recording the sound and using some decoder on it be likely to decypher anything? I guess the RTL-SDR software will have various modes that I can use (or it will detect) at each frequency to try and figure out what type of signal is being broadcast?

Anyways, I'm jumping ahead of myself. First step is finish reading those e-books while I get my early Christmas present and exhaust the potential of the Tecsun! I think after that I will pick up a RTL-SDR kit and will be kept busy a few more years playing with that on my Linux machine. With my limited time, I will be kept busy enough with this hobby for the foreseeable future with <$100 worth of equipment!   :-+

« Last Edit: December 09, 2019, 03:10:12 pm by edy »
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Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #30 on: December 09, 2019, 05:03:41 pm »
I just downloaded the Tecsun manual, and I *hope* that Tecsun PL-310ET has a BFO!  I can't see how to activate it though.  The marketing blurb says "Special design of SSB demodulation functions, can receive amateur maritime communications and personal radio", and since HF (3-30 MHz) maritime communications use single sideband the radio will need some sort of BFO function.  This radio actually uses a SDR design, which can be very effective (or may be marginal).   One deficiency that I hadn't noticed is that on the HF bands the radio only tunes in 1KHz steps.  This is fine for AM, and for channelized SSB (such as maritime), but for ham and digital modes you may want 100Hz steps.  I see that the radio uses a 32KHz crystal for it's internal clock, and given the typical accuracy of these (perhaps +/- 20 ppm) I think that some kind of "clarifier" or fine-tune control would be useful.  Again, for regular shortwave listening this won't matter much.

Regarding frequencies and modulation, while you can find all types of modulation all across the radio frequency spectrum, the Tecsun (and other similar radios) are designed to demodulate FM when tuned to the standard FM radio broadcast bands (88-108 MHz in the USA) and perhaps the television broadcast bands (where FM is used for the audio channel, at least on the traditional non-digital frequencies).  Elsewhere, the radio will be using its AM detector.  One type of AM is SSB (Single Sideband), and the radio has a BFO (Beat Frequency Oscillator) you can enable which will let you receive these signals.  With the BFO you can also demodulate CW (Continuous Wave, used for Morse code) and FSK (Frequency Shift Keying, use for many digital modes).   Decoding these digital modes can be done by sending the audio from the radio to a computer soundcard input and running one of the many programs designed to decode one or more digital modes.  You *need* a BFO to demodulate CW, SSB, and FSK, and the cheaper receivers don't have a BFO.

This computer decoding is one reason I like the SDR dongles, since with these you don't need an audio cable and you can have direct computer control of the radio frequency and mode.  This ability can really simplify the setup and avoids many potential grounding and power supply noise-related issues.  Of course if you just want to listen to shortwave broadcast stations then these additional capabilities aren't a big deal.  But in my opinion, most of the interesting stuff in ham radio radio is going on in the digital communications domain (I've been a ham for about 45 years.)

Again, bang-for-buck when it comes to a wide-range SDR I really like the "SDR-Play RSP1A".
 
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Offline bob91343

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #31 on: December 09, 2019, 05:44:34 pm »
The frequency spectrum is broken into sections by terminology.  MW is Medium Wave, or the AM broadcast band.  Then comes SW, short wave, from 3 to 30 MHz.  This is also called HF, or High Frequency.  Then comes VHF, 30 - 300 MHz.  UHF is from 300 MHz to 3 GHz.  And so on.

In your case, your primary interest would be MW and SW/HF.  There is very little radio propagation above around 25 MHz these days.  In fact, the main range is perhaps from 5 to 15 MHz the way the ionosphere is acting.  Yes there is other stuff to hear but it's mostly noise.

As an old time ham operator I can say it's one of the most fun hobbies I have.  Last night I listened mostly to noise but contacted Hungary.  Night before, Japan and Philippines and South Africa.  It's exciting when a distant station responds to a call.  I have worked well over 300 countries, all states and all continents, including some very rare places like Eritrea and North Korea and Southern Sudan, etc.

Of course, this comes with considerable investment in time and effort and space.  Not money really, as much of my gear came from swap meets and trades.
 
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Online edy

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #32 on: December 09, 2019, 05:47:59 pm »
You are correct, I do not believe there is a BFO in the Tecsun. However, I have found some people who built their own outboard BFO for SSB reception. Here is one of the websites here:

https://wf7ihomebrew.wordpress.com/2019/06/30/outboard-bfo-to-add-ssb-capability-to-am-radios/

And here is the schematic:



And built in a tin:



A fun little project if I want to start exploring this area as well! I will check out the SDR-Play RSP1A. It seemed a bit pricier than the RTL-SDR.COM V3 option (they have a full kit for <$30) but it's probably much better. So many options, so much fun to be had, so little time!   :scared:  Wow. More excited than ever!  :-+
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Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #33 on: December 09, 2019, 06:37:45 pm »
I will check out the SDR-Play RSP1A. It seemed a bit pricier than the RTL-SDR.COM V3 option (they have a full kit for <$30) but it's probably much better. So many options, so much fun to be had, so little time!   :scared:  Wow. More excited than ever!  :-+

The RTL-SDR V3 has essentially no input filtering, and when used on the HF bands it is in a "direct sampling" mode which samples the RF input at 28.8 MHz.  Without an external filter this leads to pretty terrible "aliasing" artifacts, where input signals above 14.4 MHz get "folded" back down to the 0-14 MHz region. 

As an experiment I built a receiver / digital gateway for one of the ham digital modes ("JS8" on 10.130 MHz) using one of these SDRs and a Raspberry Pi.  With external filtering and a preamp it works reasonably well.  Here is a presentation I gave to my local ham club that has some details on the SDR and how I put it all together: http://wb6cxc.com/wp-content/uploads/2019/04/Presentation-1-0.pdf  This is a narrow-band system operating on a single frequency, and it would be more difficult to turn this into a useful general-coverage receiver.  The SDR-Play and Funcube SDRs do all this filtering and conversion stuff for you and they do a darn good job of it.  The cool thing about the RTL-SDR V3 dongle is that it works in the HF band at all, is very cheap, and has a reasonably stable oscillator.

You can certainly build an external BFO, but making one that is tunable and stable can be a challenge.  These days I would use digital synthesis for the VFO, and the parts would cost me under $10.  One problem with the external VFO concept is that it doesn't give you "opposite sideband rejection".  You can still tune in a SSB signal, but you will get more background noise and potential interference.

But don't let me discourage you from building stuff!  That can be a lot of fun and a great way to learn.  One of the simplest receivers you can build is a "direct conversion" design, consisting of a BFO, a mixer, and an audio amplifier.  With just a very small handful of parts you can put together a receiver for AM and SSB.  I love designing and discussing this stuff, so feel free to ask any questions you like.
 

Online edy

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #34 on: December 12, 2019, 03:19:32 am »
I'm continuing to read through some basic radio electronics books because I'd like to understand what is going on. I know it is probably more technical than someone needs to know just to get licensed and involved in amateur radio, but for my own education I would like to really be able to start building some basic stuff to understand how it works. Right now I'm working through a series on the website http://www.learnabout-electronics.org/Oscillators/osc10.php on oscillators. I am looking at the LC tank circuit and the equation for frequency looked very familiar. It looks like that of a simple pendulum:



Compare to....



I find this fascinating. Probably no surprise to most of you. Is there some analogy one could make with L/g and LC to help learn out things from one to the other? Note that this is the small-angle approximation for pendulum. I wonder if the "angle" limitation also is analogous to some parameter that we need to keep small for an LC tank, otherwise the approximation formula no longer works? I feel that the relationship is like kinetic and potential energy being transferred back and forth. The capacitor stores potential energy, and the inductor is the kinetic.

I spoke to someone who said an outboard BFO will not work on a radio like the PL-310ET because of DSP (or probably most modern radios). Since the output of a CW being received by a radio sounds silent (since there is no modulation on top of the CW) and because of DSP handling all the audio before it even gets to the speaker, the BFO would have to be wired into the board internal to the radio where you can somehow patch it in after the receiver most likely converts the signal to the intermediate frequency the radio uses, but before the 2nd detector (demodulator) kicks in to pull out the audio from the CW (https://en.wikipedia.org/wiki/Beat_frequency_oscillator). In this case the beat is analogous to when you are tuning a guitar and you use 2 adjacent strings... you can hear a "beating" if the strings are not same frequencies which gets less and less until they are in tune to each other?

I'm also trying to understand SSB.... there is USB/LSB. My understanding is that there is a frequency "X" which is being "tuned" to. However, the LSB is being transmitted about 3 kHz below and USB is at 3 kHz above. So are we really just tuning to a frequency X-3 or X+3? If your radio has sharp enough resolution to tune to minute frequency steps, could you just tune into the LSB or USB frequency on your way through the spectrum? Or are you actually tuning to "X" and using some kind of method to pull out stuff that is slightly below or above that is not exactly tuning? For example if you had a trim somewhere in your radio for calibrating frequencies and it was off by 3 kHz in say the down direction, would you be tuning in the LSB every time you jump to certain frequencies you thought were in the middle (e.g. "X")? My confusion is in that frequencies have a "bandwidth" and not exact, and how it is that some signals can be pushed lower or higher yet we still say we are tuned to a frequency. Oh so much to learn!

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Offline bob91343

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #35 on: December 12, 2019, 04:07:37 am »
USB and LSB are opposite.  If you analyze the spectrum of an amplitude modulated signal you find a carrier wave with two sidebands, one on either frequency side of the carrier.

For a low frequency tone modulation, there will be two side frequencies close to the carrier.  For a slightly higher modulation frequency, the side frequencies move farther from the carrier, spaced from it by the modulating wave's frequency.

It was obvious that the carrier wave carried no information so circuits were devised to avoid transmitting it to allow more power to be put into the sidebands.  But since both sidebands are identical, circuits were devised to eliminate one or the other.  This is called SSB, single sideband.  In order to detect the signal, one must reinsert the carrier signal locally in the receiver.  If you are receiving upper sideband, USB, you carefully reinsert a local carrier signal at a frequency just below the signal, where the carrier signal would have been.  For LSB you reinsert the carrier on the high frequency side.

The frequency of the local signal is very critical.  To get intellligible speech, its frequency must be within perhaps 50 or 100 Hz from where it should be.  If too far from the sideband, the signal sounds high pitch and unnatural.  If too close, it really gets unintelligible due to the 'folding' of the low frequencies.

If you don't reinsert carrier, you get garble.  It takes a practiced hand to tune the local oscillator satisfactorily.  It's kind of fun, too.

Most good receivers have 'brick wall' filters in the IF so you can tune just one sideband's worth of signal.  Another benefit of this system is that it occupies half the spectrum that an AM signal occupies.  As a net result, for the same power you get about 9 dB more received signal.  And because, for speech at least, the average power is much lower than the peak power, you can gain even more by taxing the amplifier a bit more, since it won't overheat as soon.

That means that today's radio amateur can produce a signal that is perhaps 10 or more times the power than back in the old AM days, and with more compact equipment.
 

Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #36 on: December 12, 2019, 04:10:08 am »
I spoke to someone who said an outboard BFO will not work on a radio like the PL-310ET because of DSP (or probably most modern radios). Since the output of a CW being received by a radio sounds silent (since there is no modulation on top of the CW) and because of DSP handling all the audio before it even gets to the speaker, the BFO would have to be wired into the board internal to the radio where you can somehow patch it in after the receiver most likely converts the signal to the intermediate frequency the radio uses, but before the 2nd detector (demodulator) kicks in to pull out the audio from the CW (https://en.wikipedia.org/wiki/Beat_frequency_oscillator). In this case the beat is analogous to when you are tuning a guitar and you use 2 adjacent strings... you can hear a "beating" if the strings are not same frequencies which gets less and less until they are in tune to each other?

Probably correct about not being able to use an external BFO with the PL-310ET.  It is remotely possible to inject a strong signal at the radio input, offset the right amount from the desired input, and through overload the two signals will mix and generate the desired beat frequency.  But that's not really practical, and that BFO you were looking at is designed to be injected at an internal point in the (fixed-frequency) IF (intermediate frequency) signal chain.  DSP radios such as the PL-310 don't have such an IF chain, even in the digital domain.  Instead, the input signal is directly mixed down to DC (well the audio range anyway) and the traditional filtering is done via quadrature mixing and signal processing.  It's really quite elegant, and now practical because of cheap digital technology.

Quote
I'm also trying to understand SSB.... there is USB/LSB. My understanding is that there is a frequency "X" which is being "tuned" to. However, the LSB is being transmitted about 3 kHz below and USB is at 3 kHz above. So are we really just tuning to a frequency X-3 or X+3? If your radio has sharp enough resolution to tune to minute frequency steps, could you just tune into the LSB or USB frequency on your way through the spectrum? Or are you actually tuning to "X" and using some kind of method to pull out stuff that is slightly below or above that is not exactly tuning? For example if you had a trim somewhere in your radio for calibrating frequencies and it was off by 3 kHz in say the down direction, would you be tuning in the LSB every time you jump to certain frequencies you thought were in the middle (e.g. "X")? My confusion is in that frequencies have a "bandwidth" and not exact, and how it is that some signals can be pushed lower or higher yet we still say we are tuned to a frequency. Oh so much to learn!

First you need to understand AM modulation.  Here we take a carrier signal at "frequency X" and use an audio (or digital) signal to increase or decrease the amplitude of the carrier signal. Wikipedia has a good article on this, and here's one with less math: https://www.electronics-notes.com/articles/radio/modulation/amplitude-modulation-am.php.  This modulation process generates sidebands.  With a 1 KHz modulation signal, sum and difference products (sidebands) will be generated at "X+1KHz" and "X-1KHz".  The carrier is also transmitted in AM.  A basic AM receiver can demodulate this AM signal -- this can be as simple as a diode and headphones (you need a strong signal for this to work).  With Single Sideband the carrier and one of the sidebands are eliminated, and only one sideband is transmitted.  This was traditionally done with filters, and occasionally with analog phasing techniques.  These days this can be done with DSP.  Wikipedia and the link above also have discussions of SSB.  The BFO is used to essentially re-insert the carrier signal at the detector, modulating the SSB signal to produce the original audio.  Mixing (modulating) "X" and "X+1KHz" gives you sum and difference products: "2X+1KHz" (which we discard) and "1KHz" (your original audio modulating signal).
 

Online eti

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #37 on: December 12, 2019, 04:19:14 am »
I'll give you a guess which rock-solid, simple communication system based on physics and not on endless chains of servers and switches, I'd pick to save the life of my family, come a nuclear war? It's pretty simple, and here's a hint; it AIN'T the internet. We think we're SO SO "clever" and we are, but then radio preceded the "ever so pleased with itself" internet by MANY, MANY decades, and they don't use Skype or FaceTime to pilot submarines, so there's a clue as to which is better, merely by virtue of its' simplicity.

It is true that if the Internet were to go down many of us in countries whose infrastructure is addicted to the Internet will suffer a catastrophe. You wont be able to buy food, gasoline, medicines, no nothing. You water supply may well run out and you won't have electricity from the power grid. It just needs any of the lunatic countries that hoard nuclear weapons like Russia and the USA to push the button either on purpose for by accident. The doomsday clock is only TWO MINUTES TO MIDNIGHT. Nuclear attack might not be a matter of if, but when: https://en.wikipedia.org/wiki/List_of_nuclear_close_calls

But if you have a ham radio you will be able to communicate, assuming your infrastructure is destroyed and you were not vaporised. If this sounds far fetched, look what happened in Cyclone Tracey in 1974 which wiped out an entire city of Darwin. Ham radio was the ONLY form of communication to the outside world for several days. The main link was between a ham with a generator in Darwin and a ham in Melbourne.
 
If the doomsday happens, ham radio could also be used to coordinate emergency relief. And be used as an aid to hunt down the leaders of the countries that fired the nukes.

A film worth seeing is the 1964 film "Fail Safe". Such a scenario it is very possible. It almost happened in 1983.

Tell this to captain cynical in the post above you ^
 

Online edy

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?ok thanks
« Reply #38 on: December 12, 2019, 12:36:45 pm »
Ok thanks, now I got it. I read a few articles on electronics-notes.com which explained it. So in a mix of pure frequence X (carrier) plus Y (modulator) you get X+/-Y. In cases where Y is also a simple wave at a specific frequency you get a peak at each side of the X. But since audio has a range of frequencies that are modulating the peaks flatten out into bands so these 2 bands (LSB and USB) are representing the audio and carry the actual information. Part of my confusion stems from the visualization of frequency spectrum and wrapping my head around the simple AM wave graph showing a simple carrier wave with the amplitude of it being "enveloped" by the modulating wave (audio input). When you look at that diagram you can't really imagine other frequencies... all you see is the CW with a modulation, you don't see the side and frequency visually. Although peaks and valleys combine in such a way that you can end up producing signals that can be Fourier transformed to represent those other frequencies. That also explains channel spacing and other stuff.
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Online xrunner

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #39 on: December 12, 2019, 03:02:54 pm »
Your other questions have been answered, but here's some trivia about the sideband practices on the HF bands.

The tradition of using LSB below 10 MHz, and USB above 10 MHz, goes back to the very early days of SSB. Early rigs had very simple designs and an IF of 10.7 MHz. These radios passed the lower sideband below the IF frequency, and the upper sideband above the IF frequency. There was no option to choose a particular sideband as there is now. That old limitation has become the standard. But of course it's not illegal to use any sideband you wish on any band.
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Online bd139

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #40 on: December 12, 2019, 04:00:01 pm »
Yes we've got some locals on 80m here who like to use USB for some reason. I haven't worked out why.
 

Online Sal Ammoniac

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #41 on: December 12, 2019, 06:22:31 pm »
Your other questions have been answered, but here's some trivia about the sideband practices on the HF bands.

The tradition of using LSB below 10 MHz, and USB above 10 MHz, goes back to the very early days of SSB. Early rigs had very simple designs and an IF of 10.7 MHz. These radios passed the lower sideband below the IF frequency, and the upper sideband above the IF frequency. There was no option to choose a particular sideband as there is now. That old limitation has become the standard. But of course it's not illegal to use any sideband you wish on any band.


Caveat: those sideband practices on the "HF" bands that you describe only apply to the ham bands. Other users of SSB on HF, with very rare exceptions, always use USB regardless of the frequency.
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Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #42 on: December 12, 2019, 06:41:33 pm »
Most (all?) of the FSK-style digital modes use USB on the HF ham bands.  However, this is USB in name only, as the actual transmitted signal is a single frequency, or multiple single-frequency signals that are individually modulated in frequency and/or amplitude and/or phase.  The only thing "USB" about them is that they are usually generated by sending an audio "baseband" signal into a SSB transceiver (set for upper sideband), and received in the same way.  These signals can also (and sometimes are) generated directly at the output frequency by simple frequency-shifting oscillators -- no sidebands.

Actually, even these signals have sidebands.  In the case of the WSPR mode, the modulation rate (Baud rate) is 1.4648 Hz (yes, that's quite slow), and there will be upper and lower sidebands spreading out from these signals spaced at 2x the baud rate.  These fall off quite quickly, so the occupied bandwidth is very small.

The same holds true for analog frequency-shift modulation such as marine WFAX (weather facsimile charts) on the HF bands.  Your receiver will be in USB mode, and the shifting frequency signal will be converted to an analog baseband audio tone, varying a couple of KHz.  The signal isn't *really* USB, but that's how we receive it to get the demodulated audio right-side-up.  If we were to receive in LSB mode, then black would decode as white (and the synchronization signals wouldn't work).
 

Offline james_s

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #43 on: December 12, 2019, 06:48:11 pm »
I have a Grundig that I've been fairly happy with but if you want something cheaper I'd say read the reviews on Amazon, you can get something decent for not much money these days.

Shortwave is definitely not what it used to be, mostly just dead air these days. I do enjoy picking up and identifying LW NDBs used for air traffic, and as of a few years ago I was still able to find a "numbers" station which I believe was broadcasting out of Cuba, there used to be loads of those used for transmitting covert messages to spies, it was a lot of fun to hunt for them. Occasionally I hear local hams yakking about their medical problems and every now and then there's still some foreign broadcast. Oh and of course WWV/WWVH is still around for now anyway.
 

Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #44 on: December 12, 2019, 07:02:12 pm »
You are correct, I do not believe there is a BFO in the Tecsun.

Back to that Tecsun, the marketing blurb says: "Special design of SSB demodulation functions, can receive amateur maritime communications and personal radio".  So I think we should expect that you will be able to receive SSB.  Please let us know how this works for you!  We can give you some pointers to help you find SSB signals to monitor.
 

Online PA0PBZ

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #45 on: December 12, 2019, 07:20:26 pm »
Back to that Tecsun, the marketing blurb says: "Special design of SSB demodulation functions, can receive amateur maritime communications and personal radio".  So I think we should expect that you will be able to receive SSB.  Please let us know how this works for you!  We can give you some pointers to help you find SSB signals to monitor.

I found this only on Amazon and it must be a mistake. In a few reviews (eham.net) they mention it has no SSB capability and since this is a direct sampling radio you can't build an oscillator on the IF frequency (there is no IF). Also, the tuning steps are way too big for SSB.
« Last Edit: December 12, 2019, 07:22:25 pm by PA0PBZ »
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Offline fourfathom

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #46 on: December 12, 2019, 08:13:39 pm »
Back to that Tecsun, the marketing blurb says: "Special design of SSB demodulation functions, can receive amateur maritime communications and personal radio".  So I think we should expect that you will be able to receive SSB.  Please let us know how this works for you!  We can give you some pointers to help you find SSB signals to monitor.

I found this only on Amazon and it must be a mistake. In a few reviews (eham.net) they mention it has no SSB capability and since this is a direct sampling radio you can't build an oscillator on the IF frequency (there is no IF). Also, the tuning steps are way too big for SSB.

I agree on the tuning steps, although for channelized marine SSB they might be OK -- assuming that the radio oscillator is accurate.  Since the diagram in the manual shows a 32KHz xtal as the SDR reference clock, I would guess that the accuracy isn't all that good and you would need a "clarifier" (fine-tuning) to make it usable on SSB.  It is certainly possible to demodulate SSB on an SDR radio, the BFO is implemented in DSP.  But you still need 100Hz or finer tuning steps for non-channelized SSB.
 

Online edy

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #47 on: December 12, 2019, 10:00:34 pm »
I've been thinking more about sidebands. I understand beats fairly well, I can visualize how 2 frequencies that differ slightly will interfere and because they are slightly off they will originally constructively interfere and produce 2x peaks, and then a moment later they will be out of phase (180 degrees) and will cancel out completely. So by combining 2 very-close frequencies you get the beat pattern... and the beat frequency increases as the difference between frequencies gets bigger.... and I have intuitive experience with this as well with tuning guitar strings as you try to tune adjacent strings by playing same note and listening for the beats to try and minimize the beats.

To understand the sideband production (when modulating a single CW) I am trying to intuitively understand what is happening, so I flipped it BACKWARDS... and imagine what would happen if you combine a sideband with it's CW. Say if I combine the LSB with CW, then I would pull out the "beats" which in this case ends up giving us the actual audio signal. Similarly, I can combine a USB with the CW and it will create "beats" as well, which is the audio signal. So I understand it in terms of demodulation....  how the beats will come out of combining either LSB+CW or USB+CW. The other way is harder to wrap my head around (how combining CW+modulation generates beats). This video is great to demonstrate it:



I am going to try and use Audacity to generate waveforms and combine them. I can generate a tone of a very high frequency (CW) and then a lower frequency tone (modulation) and I believe there are Nyquist filters/functions or coding you can do in Audacity to let you modify one wave using the other. Then I can run it through a spectrum analysis in Audacity and see if it produces the kind of peak patterns that we see in that video.

I should also be able to programmatically create a WAVE file. If I can make a RAW file which is essentially just a string of 16 or 32-bit values, I can write out a sine wave and modulate it all in software. I'll have to see the format for writing out RAW wave data and then should be able to write a small C program to do it and test out different things.

Regarding the Tecsun, here is the spec sheet:

https://www.tecsunradios.com.au/store/product/tecsun-pl310et-multi-band-radio/

It says it has selectable IF bandwidth. I don't know what that exactly means. Maybe there are some software-enabled DSP functions for specific frequency ranges that give you some SSB capability. I don't know. Seems to be all done by the chips and there may be a PGA in there with custom firmware doing stuff. I have no idea how these radios are built and haven't yet looked at the block diagram or schematic.
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Offline Bud

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #48 on: December 12, 2019, 10:21:40 pm »
You are correct, I do not believe there is a BFO in the Tecsun.

Back to that Tecsun, the marketing blurb says: "Special design of SSB demodulation functions, can receive amateur maritime communications and personal radio".  So I think we should expect that you will be able to receive SSB.  Please let us know how this works for you!  We can give you some pointers to help you find SSB signals to monitor.
What is "amateur maritime communication" ?
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Offline james_s

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Re: Any Shortware Radio Tips for a Noob Considering the Hobby?
« Reply #49 on: December 12, 2019, 10:58:57 pm »
You are correct, I do not believe there is a BFO in the Tecsun.

Back to that Tecsun, the marketing blurb says: "Special design of SSB demodulation functions, can receive amateur maritime communications and personal radio".  So I think we should expect that you will be able to receive SSB.  Please let us know how this works for you!  We can give you some pointers to help you find SSB signals to monitor.
What is "amateur maritime communication" ?

It's used for communicating between private ocean going boats mostly. My dad's sailboat came with a SSB transceiver and an old packet modem installed. Previously it was owned by a couple who sailed it all over the world. They used the SSB radio to communicate longer distances than the marine VHF.
 


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