Ham Radio / Off-grid communication

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Thank you to everyone who participated in the JS8call Kiwi Bulletin!

I logged 5 calls, NVA3FY, G0Y, KOK0A, someone transmitting with no call "SNEED" and another one I forgot to write down, my bad.

If you have a QSL report feel free to post it in the thread or DM it to me. Pretty good for an ad-hoc bulletin with only a few days of notice. Unfortunately the 23:00 window and 01:00 didn't seem to make it to most of Europe though.

20 meters seems to be a good fit for North America during the evening, and reaching parts of Europe towards dusk. For future bulletins we might use a combo of 20 and 40 for more reliable propagation. The idea for the 23:00 window was to use greyline prop. But that has a very narrow reach. I could spot the bulletin in SDRs in Ireland, France, and the Netherlands but couldn't anywhere east of that.

My setup was 25 watts of power and a 24 ft random wire antenna @ 18 ft. Next time, I will try to get it much higher up in the air but didn't have a mast with me to deploy. I'm also building a pallet amp and may have a 20m Hexbeam coming soon.

hog cranking frog dijo:
Anyone have any interest in a old school over the air BBS?
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This is the next step of the master plan. Once we can get a few people on the air with reliable enough setups we could start doing some crazy stuff with higher throughput digimodes like running store and forward BBS software.
 
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I set the software to 4 pass decoding for tx 3. Pretty impressive for 25W.
 
Jotch dijo:
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WTF is happening on 40m right now, I have no idea what this signal is but I've seen it before, the sound is familiar when mapped to LSB/USB, 10kHz wide with tight tolerance.
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Digital Radio Mondiale (DRM) 7205 kHz AM China Radio International. They use 9 gajillion watts of power and usually it's only there for like 30 minute slots or so. DRM is an encoding scheme for commercial shortwave broadcasters https://www.sigidwiki.com/wiki/Digital_Radio_Mondiale_(DRM) https://www.drm.org/about-drm/drm-technology/ but it's really only used in Asia.

You can use the DRM (not be confused with DMR or digital rights management) plugin on KiwiSDRs or dream to decode and listen if you want.

Too much random shit in 40m which is why MARS modding your radio is based, fuck da band plans

Btw, did you have a reception report from yesterday's Kiwi Bulletin?
 
888Flux dijo:
Digital Radio Mondiale (DRM) 7205 kHz AM China Radio International. They use 9 gajillion watts of power and usually it's only there for like 30 minute slots or so. DRM is an encoding scheme for commercial shortwave broadcasters https://www.sigidwiki.com/wiki/Digital_Radio_Mondiale_(DRM) https://www.drm.org/about-drm/drm-technology/ but it's really only used in Asia.

You can use the DRM (not be confused with DMR or digital rights management) plugin on KiwiSDRs or dream to decode and listen if you want.

Too much random shit in 40m which is why MARS modding your radio is based, fuck da band plans

Btw, did you have a reception report from yesterday's Kiwi Bulletin?
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Thank you! This explains it completely.
I recieved most of the bulletin from the later broadcasts, you came in -12 over -20 at peak but faded in and out. Early broadcast faded completely and was not recovered after 10 mins.
I think if I put the two receptions together I could get a complete broadcast.

Is there any practical benefit for using slower JS8CALL modes? Why not always use turbo if it's FSK and just a matter of bandwidth? Since at any given time you're putting out CW.
 
Jotch dijo:
Is there any practical benefit for using slower JS8CALL modes? Why not always use turbo if it's FSK and just a matter of bandwidth?
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The signal margi,n. JS8 normal works down to -28 dB, slow I've seen as low as -30 dB, while JS8 Turbo has a floor of -18 dB. A difference of 10 dB here is a factor of 10 in power.

Each time you double the symbol duration each tone occupies half the bandwidth. Half of the noise is working against the signal while the signal energy per symbol would stay the same as you increase bandwidth. JS8 Turbo uses a bandwidth of 160 Hz compared to normals 50 Hz, while Slow uses 25 Hz.

Generally modes with higher throughput require higher SNRs / energy per bit to be decoded.
 
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hog cranking frog dijo:
You guys are making me want to bring out my fan dipole and get back on the air.
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I've been meaning to get my amateur radio license for years, but I just haven't gotten around to it. This thread and the JS8Call stuff @888Flux is making that itch flare up again. Though I'm not optimistic about getting a signal where I am. Even with a big chungus antenna, on account of being on the opposite side of North America to Europe, and the understandably directional nature of the transmissions.

I also suspect there wouldn't be enough Ausfags and SEAfags to justify transmissions in this direction.

Even without the chance of joining in the KFALL fun, I should get the license anyway so I can tick that box on my Shit To Do Before I Die list.
 
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Pee Cola dijo:
Even with a big chungus antenna, on account of being on the opposite side of North America to Europe, and the understandably directional nature of the transmissions.
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Part of it was operator error. The goal of this was to mainly experiment and see just where the signal could reach.

My setup was my random wire antenna sloping down at only 18 ft high. The best height for DX'ing is getting the antenna above 1/2 of the wavelength for the operating frequency. For 20 meters that's 10 meters, and in burger units thats 32 ft.

The 20 meter bands would work for the US, and I could spot myself on web SDRs over in parts of Europe like Ireland, but to really maximize effectiveness for broadcasting the bulletin I'm going to get equipped with a better setup. Also just got a mast out of storage and that's ready to be setup now which will solve the antenna height issue.

Another issue I had was the balun for the random wire antenna. JS8call has a duty cycle of 100% on transmit. The transformer would heat up and cause the SWR to creep towards 2.5 which meant I had to be transmitting under 50 watts. The one I have I DIY'd but I'm buying a off the shelf one that is rated for 1 kW to see if that solves that issue. That will allow me to increase transmit power up to around 75 watts. I'm also building a pallet amp but dunno if that will be necessary.

The next JS8 bulletin/net is going to use a combo of the 40 meter bands and 20 meter bands. 40 meters will have a much better shot at longer distances. I bet that most people who had trouble picking it up last time will be able to get it on 40 once I have my setup all sorted out.

There is a high likelihood next time, with just with a simple active mag loop or wire antenna that you could stick outside you would be able to receive it.


What is everyone thinking for the schedule of the JS8 net? Would you like to see this be a monthly thing?
 
888Flux dijo:
There is a high likelihood next time, with just with a simple active mag loop or wire antenna that you could stick outside you would be able to receive it.
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I'm fortunate enough to have a decent sized property, so putting up a 10m / 32ft mast would be doable. In fact I know someone with an old telescopic TV antenna mast they no longer use and I was going to take it off their hands. Mainly for the purposes of setting up a low power FM station for my own amusement (I love the idea of hearing MATI over FM), but it'd be handy for amateur band / SW / DXing too. Could take a while to set that up though.

I have an RTL2832-based USB DVB-T stick that can be repurposed for RTL-SDR, so I was going to use that along with a simple antenna like the ones you've described as my initial receiver.
 
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