Ham Radio / Off-grid communication

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Oh if you want to tinker and work CW, just make a Michigan Mighty Mite!

And yeah, the mystery of getting on the air has been largely overblown. Seriously, the amount of stuff you can do with a UV-5R is crazy and half of all these antenna builds are optimizing, not "just getting it working" levels of precision.
 
WanderingFarmer dijo:
Oh if you want to tinker and work CW, just make a Michigan Mighty Mite!

And yeah, the mystery of getting on the air has been largely overblown. Seriously, the amount of stuff you can do with a UV-5R is crazy and half of all these antenna builds are optimizing, not "just getting it working" levels of precision.
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Really cool and accessible for teenagers, but I really like the idea of doing direct RF synthesis.
I'm very familiar with FPGAs and a bit familiar with DSP in general.
You can easily have processing clock rates of 200 MHZ in those chips, which is precision to the nearest 20th the wave in the case of the 40m band.
This is completely ignoring any SIMD tricks you can pull off to boost the effective rate.
 
Jotch dijo:
Really cool and accessible for teenagers, but I really like the idea of doing direct RF synthesis.
I'm very familiar with FPGAs and a bit familiar with DSP in general.
You can easily have processing clock rates of 200 MHZ in those chips, which is precision to the nearest 20th the wave in the case of the 40m band.
This is completely ignoring any SIMD tricks you can pull off to boost the effective rate.
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More power to ya! Keep us posted how the build and test go.
I'm barely at the build a kit radio and build a pc stage of understanding electronics here, so the idea of doing that makes me clutch my chinesium brick tighter.
 
Jotch dijo:
I'm very familiar with FPGAs and a bit familiar with DSP in general.
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This may be of interest:

Also there is a more affordable (and fairly decent) Chinesium clone of it too:

A project I was working on in the past was trying to make this into a full fledged transceiver for MIMO applications on the HF spectrum based on this:
1756950640476.webp
 
Some updates to my DIY radio. Direct output from the FPGA into a R/2R resistor ladder as a quick and free (already had them) 8 bit DAC.

On my scope I see a pretty clean looking wave, but on my SDR it has massive amounts of splatter to the sides of it. Even from 50 feet away this 5mW transmitter (Slow slew, 4mA, 3.3V) splatters across the entire 40m HAM band. This is all radiated from a 3 inch length of wire between the FPGA and the scope.

Why is it so messy? I know the 1% resistors probably aren't going to cut a smooth wave but I wasn't expecting 500k bandwidth.

I often think if this is even possible on a small budget, given decent radios costing $600+,
though I wonder if that cost is the cost of not only the transmitter; but also the reciever, complex processing electronics for waterfall, the ability to tune without reprogramming the whole thing, and FCC certification. Wheras my thing lacks all of those latter ones.

Either way I was able to pull off DSBSC on multiple sine waves in the device, or AM that can be picked up by normal radios, now to hook up my microphone ADC and see if that works...

Then try getting proper SSB by LP/HP filtering the DSB-SC output with FIR filters, then a proper low noise DAC...
Optimistically, if everything looks perfect, I could possibly pick up an amplifier that can work with 10mW input and see if I can get ahold of someone on my monstrosity.
 
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Jotch dijo:
Why is it so messy? I know the 1% resistors probably aren't going to cut a smooth wave but I wasn't expecting 500k bandwidth.
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You've achieved accidental resonance it sounds like! I'm just guessing here though.
Jotch dijo:
I often think if this is even possible on a small budget, given decent radios costing $600+,
though I wonder if that cost is the cost of not only the transmitter; but also the reciever, complex processing electronics for waterfall, the ability to tune without reprogramming the whole thing, and FCC certification. Wheras my thing lacks all of those latter ones.
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I started looking into this more over the past week and you're on the right train of thought there. Receivers are surprisingly complex pieces of tech and given all the attention the extra class manual gives to receivers and receiver tech I'd be willing to bet the receiver part of a transceiver is the more expensive part.
I think it can be done for less than $600, I'll even say less than $200, but you might have to limit yourself to specific bands for saving money.
Jotch dijo:
Either way I was able to pull off DSBSC on multiple sine waves in the device, or AM that can be picked up by normal radios, now to hook up my microphone ADC and see if that works...

Then try getting proper SSB by LP/HP filtering the DSB-SC output with FIR filters, then a proper low noise DAC...
Optimistically, if everything looks perfect, I could possibly pick up an amplifier that can work with 10mW input and see if I can get ahold of someone on my monstrosity.
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Best of luck! A buddy of mine is building a kit radio and during his test he wasn't able to receive me on 20, 40, or 10m and he couldn't transmit either, so you're at least transmitting... if a bit wider than expected.
 
WanderingFarmer dijo:
You've achieved accidental resonance it sounds like! I'm just guessing here though.
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I think you're right, would explain the unusual strength.
I ran this by a RF guy I know and he says the wide emission is because the wire is not the only part emitting, but the sharp edges of digital input going into the DAC are also emitting. Particularly the traces inside the breadboard between the FPGA and the resistors.
I'll see what happens if I put the whole thing into a gutted PSU box with a ground.
I'm hoping I can keep this whole construction under $50 (minus the $150 FPGA devkit, but that's not dedicated to this project, and also the hundreds of dollars amplifier).

Thanks for the other advice!
 
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I've, at last, got the authorization from HOA to put antennas on the balcony, so I'll put up my VHF/UHF home setup back on the air. (+ an SWL antenna. Thinking about MLA-30 but open to any suggestions)

Read about a 23 cm mod for the venerable UV-K5, which instantly grabbed my attention. From what I understand, the firmware was done by a Russian guy (Xenomorph) and the hardware modifications were done by some Bulgarian hams (LZ3HD and LZ5HP, who has a bit of a reputation building 23 cm band stuff). If I manage to clear house on half-finished things soon, this will definitely be my winter project.

888Flux dijo:
For using HF radio as an interface, I made a codec2 wrapper that operates as a software modem. You can find the link to that here The instructions are contained in the README but if you need any help feel free to ask.
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Absolute mad lad, definitely going to dick around with this. Have you tested COFDMTV by any chance ?
 
Juan Números dijo:
Have you tested COFDMTV by any chance ?
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I haven't, though it looks interesting. Mercury is a similar project and was designed with physical parameters for the HF bands.

There is a severe lack of open source, performant (>4800 bps) modem software for HF use. Even for military and commercial applications none of the modern telecom stuff has been brought over. It's something that seems to be stuck in 1999.
AnOminous dijo:
SSTV I assume.
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SSTV but did you know you can also draw pictures on the waterfall itself?
 
888Flux dijo:
There is a severe lack of open source, performant (>4800 bps) modem software for HF use. Even for military and commercial applications none of the modern telecom stuff has been brought over. It's something that seems to be stuck in 1999.
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Expectations spoiled by the colossal abundance of bandwidth in the UHF and SHF bands. A single WiFi channel shifted down to 3Mhz would cover the entire HF spectrum and spill over into VHF, and it wouldn't function at all.

You see so many things limited to ~4800bps because that's what you can reliably fit into the 2.5-3khz or so bandwidth you get out of a SSB transceiver.
 
all democrats love penis juice
 
Polock dijo:
However you'd need to spoonfeed me how to set it up.
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There are 2 scenarios for setting up JS8CALL:
1. You have used digital modes before, have WSJT-X installed, and know how to operate FT8
2. You know you can connect a radio to a computer and it makes the funny noises at the bottom of the band mean something.


1. All you have to do is install JS8CALL on the same drive as WSJT-X. It'll use your config settings to get up and going with no further work from you. At launch, just enter the information you want displayed (it does require you to enter characters in the correct format of a callsign and grid locator) and then what call groups you want to listen for.
2. Let's assume you want to set this up for the prospective KFNET so in the field "Callsign Groups" you'll add '@KFALL' at the very least. This lets you filter out anyone else transmitting to just those focusing their transmissions for everyone else focusing on that callsign group. after that, add a comma and any other groups you want to listen out for.
3. Under that field you'll see a check box, that's to opt out of the '@ALLCALL' group, but I've found it useful to have it so i know my decode is working.
4. The next group of fields is just pre-loading responses to cut down on typing. I don't believe any one can hold the entire bee movie script, but I haven't tried. Once you've set those up how you like them (or you leave them as is) you can click okay and get started fiddling with the UI.
5. Click and drag the waterfall down low, you need to maximize the top of the window where you have decoded messages on the left, Filtered messages (whatever callsign group or callsign you have selected) in the middle in an off-beige box, and your typing window directly below that. On the right is a box with all the callsign groups you added in initial set-up and the callsign of anyone transmitting.
6. To focus your Rx and Tx, click a callsign group, or a callsign. Type your message in the text box, then click enter. Your radio should now spend the next 30-45sec cycling transmit and decode till your message is sent. This does mean that the longer the message the longer you'll have to wait for it to send and fully decode. It's important to realize that you'll not get a full sentence in one burst, but it should be done in a minute or two. The net will be a great test as to how long long form messages take to send.
This should be enough to get you up and going. use the same tuning and software side adjustments you'd use to fine-tune your FT8 decoding and transmitting.


So that's the easy way. If you've never tried digital modes before, well setting up WSJT-X varies a little from radio to radio, so you'll probably want to pull up a radio specific guide. Reply to this post with your set up and I'll try my best to link you in the right direction. In general though:


1. You'll need to start by installing WSJT-X and it's dependencies. Finish the install then deselect "launch WSJT-X" and close out the window. Launching WSJT-X without a radio attached is just going generate an error that makes you close the program anyways.
2. Assuming your radio is multi-mode turn it on and place it in U-Digi (upper side band digital) or just USB if that's how your radio handles digital modes. Consult your manual for clarification. Digi-rig is different from both of these and I won't be covering that in this post. Happy to follow up later though if that's helpful.
3. Attach the appropriate data cable to your radio.
4. Open your device manager and navigate to the USB devices. (sometimes hidden in Windows) or CLI if you know the script for showing connected USB devices.
5. Plug the computer end of the data cable into your computer. Locate the new device by your preferred method. This is the first tricky part. Some radios show up with an A & B part as separate devices. You'll need to look up the specific instructions for your radio elsewhere or pick A, note the COM port, and hope it works. If not, there's always B. Leave this window up just in case you need to reference it again or lose your sticky note with the COM port on it.
6. Launch WSJT-X, enter your callsign and maidenhead grid location.
7. Go to the radio tab and prepare for some fiddling.
8. In the radio tab, start by selecting your radio from the drop-down list. Type in the COM port your radio is using. Leave all the other settings that have a "default" option on default. In the PTT Mode box, select CAT for control type. Data/Pkt in the Mode box, and "Fake it" in the Split Mode box.
9. Click "Test PTT" If that button goes green, congrats! Your radio plays nice with the software. If it goes red, something got screwed up. First try changing the COM port to the other one. If that fails again, change it back and proceed. Try selecting 'none' in the split mode box and try again. If that also fails, try selecting USB in the "Mode" box. If that fails, save yourself further frustration and just go look up the recommended configuration for your radio. Once you get the green light click okay and your radio should tune to the station selected for whatever mode your installation launched in (usually FT8)
10. Install JS8CALL. You might be wondering why go through all that in a different software if we're just installing the software we want 10+ steps later. JS8CALL will import your config settings, including some options that get hidden in "advanced" in JS8CALL's radio configuration step.
11. Launch JS8CALL and go up to "Spoiler 1" above.

Lastly a few tips:

If you're using linux and get a permissions error, make sure your user is added to the callout group.
Adjust your microphone input levels to be sure your received audio is between 40 - 70 db. If it's coming in too loud, you won't decode anything. This took me days to solve
Reply to this post if you're having trouble. I'm no expert, but I'll do what I can to help ya out.

I'll be happy to dive into more detail here if needed, but this should point you in the right direction, and I'm not even trying to shill amazon affiliate links!
 
I must just be lucky picking this week of all weeks to try starting a net. Get your JS8CALL software configured and ready to decode. Bring a fan or a block of dry ice to set it on for this one.

Callsign Groups to add: '@KFALL, '@KF<Country><State/Province>, '@KFOT
Be sure to remove the ' and separate each by a comma.

Frequency: 7.096, Back-up 7.033, Tertiary 7.111

Date: Saturday 9/13

Time: 2100-2130 CST, This test should only take a half hour at most. Be there at 2045 CST for test to see if you can even pick up my 5w output.


Example regional callgroup: '@KFUSAOH
KFOT is an off topic call group. I'm assuming there will be spam, and arguing thanks to recent events, but if you could do me a solid and keep it to KFOT that'd be great.

If no one can pick up my transmission, I'll have to figure out how I can get the ~$600 I'd need for the 100W amp Xiegu makes for my radio, or we change host for the next one and let a more powerful station transmit the bulletin. We'll see how it goes this weekend though!
 
Polock dijo:
>>>>Your setup
Bruh I have two UV5Rs, two jungle antennas, and a CB lmao I am only JUST getting into this, I'm still learning the basic stuff like lingo
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Well that certainly complicates things because you have to receive HF signals and the UV-5R can't do that.
You wouldn't happen to have an SDR dongle would you? That would let you receive the net and get used to listening to the lower bands (HF bands)

Just getting into this is fine and all, that's how I started, but it does limit your connectivity to line of sight. I'd recommend getting used to programming in repeaters and playing around with different antenna set ups and making your own coax cables. Get some BNC adapters like Signal Stuff sells, and see about making a yagi for satellite comms. All you need for that is two old or cheap tape measures and a soldering iron... and patience to trim things! All those skills scale up to HF, and if you can cut your own coax and put the connectors on yourself, you can set up some great 2m or 70cm antennas
 
WanderingFarmer dijo:
Time: 2100-2130 CST, This test should only take a half hour at most. Be there at 2045 CST for test to see if you can even pick up my 5w output.
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See you there. As a helpful tip for future nets, it may be better to use UTC as it makes timezone conversion quicker as you just add / subtract from your timezone. For example CST is UTC-6

My setup will be Yaesu FT-891 with a end fed half wave on a Spiderbeam mast. Probably will run at it at 25 watts

VOACAP reliability chart for San Francisco, US to Washington 9/14 0200
1757709144646.webp
 
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