I didn't want to clutter the schedule with my own comments, so I'll note them here.
Turns out tonight's broadcast was just a replay of last week's. I was surprised when it seemed like the song list was familiar and then the digital modes broadcast at 01:30 UTC was the exact same. I was expecting only two modes.
Consolation was that I had a second chance at a perfect copy of the MFSK64 schedule, and so it was. It's not legit HTML, though. I added p tags where there weren't any, closed off p tags elsewhere, and removed html/body tags at the beginning and end.
Also, the pre tag for the KBC logo was in between the beginning body and html tags.
I mentioned last week that forward error correction was good, but I don't actually know if the DominoEx 16 transmission used FEC or not. What I do know is that FEC plus frequency diversity is really good, because I was unable to receive PSK125R and DominoEx 16 error free yet again, but MFSK32 was perfect.
I don't really trust the fldigi reported SNR for frequency shift keying modes. MFSK32 and 64 were anywhere from -1 dB to +3 dB, and yet on the demod spectrum the frequency carrier to noise ratio was easily 20 dB. The PSKR modes were reporting 24 dB SNR, which is more reasonable, and yet that's not sufficient for error free reception, even though those modes use typical FEC things like convolutional codes and interleavers.
I typically use AGC when listening to anything non digital, and it can kind of mess up PSK type transmissions. So FSK has an advantage if decoding on the fly. Fortunately I remembered to record the DDC this time around so I could retry PSK with a constant gain. I was still unable to get a perfect copy. So yes, (greater) frequency diversity and FEC are a winning combination.
No comments:
Post a Comment