With a bit of luck, I may have this working by the weekend. It is a DSB RX for 10m FT8. It means the "big rig" can be used for other things and 10m FT8 can be continuously monitored.
Simple QRP projects, 10m, 8m, 6m, 4m, FT8, 160m, WSPR, LF/MF, sub-9kHz, nanowaves and other random stuff, some not related to amateur radio.
Buy me (a virtual) cup of coffee
This is NOT at all compulsory, but this would help offset some project costs.
Any donations most gratefully received.
https://ko-fi.com/rogerg3xbm
Any donations most gratefully received.
https://ko-fi.com/rogerg3xbm
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SSTV from the International Space Station (ISS)
During this week is a chance to get slow scan TV from the ISS. This video may help. SSTV is not something I have done seriously.
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6 comments:
It is a pity, indeed, to hang up a fully fledged transceiver for a single frequency.
I have some tiny single frequency 1W transceivers made for JT65 at the time. I need to find them again and pull the frequency to the FT8 frequencies. I have a set for 40, 20 and 15m, and that would be perfect for some propagation monitoring.
Vy 73 de Jan, OZ9QV
Hi Roger,
I have been experimenting with a 1W QRP DSB 1W transmitter fed from a QRPlabs QCX CW transceiver on 40m and trying FT8 and WSPR using a PC to generate the modulation. However on-air, no-one is decoding me. I can decode my own signals no problem. I can revive both modes fine on the QCX. If I use my Yaesu FT897 in lowest power mode I get loads of spots,so I know my antenna is good.
When I look at the transmitted waveform of my DSB signal it looks like an AM signal, but if I look at the QCX output in its own WSPR mode it looks like an FSK constant amplitude signal. I wonder what waveform you see from your DSB rig when transmitting FT8?
73 Ken g4apb
It is a long time since I looked at the DSB waveform. but you would expect to see the classic DSB waveform, that is like an SSB signal with 2 tones I think. Certainlt not an AM waveform that suggests too much carrier.
Hi Roger,
that is exactly my question, what should a 'classic DSB' waveform modulated with an FT8 FSK signal supposed to look like?
I must have something wrong as no spots on FT8 with my homebrew tx.
There is no carrier when no tones are fed in.
73 Ken G4APB
It should be like AM but with sharp transistions at the zero crossings. See https://electronics.stackexchange.com/questions/537013/over-amplitute-modulation-vs-dsb-sc-modulation.
Many thanks Roger,
that is exactly how my DSB signal looks, even the zero crossing phase inversions, so I must be doing that right. Got to just figure why my cq Ft8 calls dont get spotted.
73 Ken G4APB
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