On Wed, Nov 30, 2022 at 09:06 AM, Hans Summers wrote:
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Clearly QDX works extremely well already; however I do believe that use of this improved firmware version should be recommended for everyone (once I release an official 1_06, after a few people confirm there are no unintended issues with the beta version). Improved accuracy of the transmitted frequency does result in increased probability of decode, particularly under DX circumstances or other weak conditions.?
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Thusly expired my Wednesday...
Hans and all,
Since I am rather a culprit in starting this general topic I thought I should respond near its end.
First, Hans thank you so much for expending a perfectly good work day on curing this. I believe that I can concur that the fixes have worked.? I greatly appreciate that and your interest and willingness in improving the performance in this 'narrow band' domain.? I know that like myself, many others appreciate it as well.
What I'm not sure many appreciate is how important these improvements may prove to be.? I'm especially still thinking of FST4(W) but more generally in the application of narrow/long digital modes at not only LF and MF as FST4W was initially targetted but also at HF-microwave.? As you know, several of us have spent some effort in applying the mode, increasing the number of transmitting beacons and ireceive sites and seeking to better understand the characteristics and limitations. What we've found is that in some situations, perhaps many, even at mid-HF there exists the ability to decode "well behaved" transmissions in a way that may extend the performance of amateur beacon and QSO communications far more than the existing popular modes such as FT8 and WSPR.??
This can have the effect of 'digging deeper' into the noise by 10-20 dB beyond what has been the current limit.? This is several S units, the same as a 10 to 100 times increase in transmitter power and may allow investigation and QSO at times and to locations not previously possible within all of amateur radio.? Because of its performance and price point the QDX may become a key player in harnessing these new possibilities.? Not only beacon spots and? QSO? but new propagation and ionospheric study have already become a reality. Better communication and geophysical science are clearly benefitted. This potential is not limited to HF but probably is now available at VHF-microwave.? Very long DX on 2m through X band, where ionospheric limitation isn't present starts to become a reality.?
It may be that yet newer modulation formats and protocols are required to take full advantage of this but WSPR and FT8 have taken a while to catch on so with patience some really interesting possibilities may be furthered by the presence of more stations worldwide operating.? I think the QDX may be a key contributor to that future.?
I have quickly looked at v1_06_6? and have found that once I reduced the tx shift from 500 to 0, FST4W with fully GPSDO external clock substitued for the QDX's TCXO and GPSDO LOs on the receive side?produce extremely low spectral spreading.? I'm now seeing total end-end spreading well under 10 mill-Hz on 20m over LOS paths.? This is low enough to take essentially remove HW as a limitation and allows both better FST4W DX and also better examination of ionospheric, its modulation by the earth's magnetosphere, effects of CME events from the sun, travelling ionospheric waves and no doubt other effects not previously recognized.
I'm hoping that these possibilities will be recognized and that the QDX with suitable clock may greatly stimulate all of this.??
Thanks again for making these improvements !
Glenn n6gn
Fort Collins, CO
