3 Oct 2021
Little Walsingham - NOT amateur radio
20FT8R or 15FT8R anyone?
Whilst playing with the 10FT8R something occurred to me. With FT8, oscillators only have to be stable over 15 seconds. Many free running HF oscillators are far more stable than this even long term.
So, I think the crystal can be replaced by a just a tuned circuit making this receiver work on any HF FT8 frequency. All that really matters is reasonable long term stability and good short-term stability. All that's required is to scale the RF tuned circuit (one tuned circuit) and set the oscillator to half the FT8 frequency needed. I have not tried this but cannot see why it should not work.
This may work as high as VHF where I have made free running oscillators work even on 2m.
Do not be afraid to experiment!
This should make the whole receiver very low cost indeed. It would not surprise me if many can make the entire RX for less than the cost of one coffee out.
Nearly gone - NOT amateur radio
2 Oct 2021
10FT8R 10m FT8 RX
As a benchmark, I want to try first with the original design, then swap crystals but without the toroid near the crystal. I should be able to net the crystal without the toroid.
The simple direct conversion RX uses a Polyakov mixer with injection at half fequency.
See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/10ft8r-rx .
UPDATE 1400z: As expected, the even simpler circuit around the crystal works fine with plenty of South American stations immediately spotted. The map shows the stations spotted in just the last 30 minutes on the 10FT8R with the simpler circuit (no toroid) and a 14.037MHz crystal. It works. The revised circuit is shown on the photo, without the crystal T50 toroid.1971 - NOT amateur radio
50 years later I am bald and much different. Where did the years go?
Grandson's crocheting - NOT amateur radio
Old cottage - NOT amateur radio
Yesterday evening on 472kHz WSPR RX
Most of yesterday evening, I was on 472kHz WSPR RX using the FT817ND and the earth-electrode "antenna" in the ground. In all, 8 different stations were spotted with the furthermost IZ3QQG (1155km).









