Hi David and all interested
Today, the conds on 40m where usable after a long period of complete
loss of signal because the MUF was only around 6.5 MHz for 300 km.
(dc6ny is about 275 km away from my location).
But now dc6ny and i have made our first freeDV700B-qso today at about
1100 UTC.
My audio frequency filter for tx and rx was from 700 Hz to 2400 Hz for
this mode.
I noticed some very positive things:
1) the sound of the 700B mode is - at least what I remember from our
experiments a year ago -
comparable in sound quality to the 1600 mode. I was very pleased
about that. We did not test the 700 mode, but in my local experiments, I
found the 700 mode not as comfortable as the 700B. Since the modulation
scheme is the same, I assume, that 700 as no advantage over 700B?
2) As soon, as the rx-frequency is adjusted correctely, the modem locks
very quickly. In the 1600 mode it seemed to me not as quick.
3) I used about 25 to 28 Watts peak measured just before the antenna
coupler. dc6ny gave me a report of 59+ on his hpsdr system. Switching to
SSB, my peak power was between 250 and 300 W.
Question: I show the estimated SNR from the libarary on my sdr. In
1600mode I always saw about 12-20 (positive) with good signals (whatever
these figures mean). In the 700B I see a figure around -6.2 (negative)
with good signal. Probably I have made an error in the presentation?
We are planning experiments with different SNR conditions to find out
the limits of this new mode.
The first results are very encuraging!
Thank you very much for your constant effort on freeDV!
73, Alfred, hb9epu
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