On 6/23/2020 4:53 PM, Adrian wrote:
An excessive strength FT8 signal is easy to remove with notch.
Yes, BUT -- the notch introduces phase shift, which can degrade
decoding. K1JT recommends running the IF wide and letting WSJT-X
separate signals.
I DO strongly differ with the advice in the WSJT-X manual for setting
levels. Instead, I recommend setting audio gains so that the green bar
indicating audio level as close as possible to the top without it
turning red on when strong signals are present. I find Slow AGC works
well for me, because both the strongest signals AND my local noise vary
widely.
Why do I recommend this? Simple. The practical dynamic range of a 16-bit
A/D is about 90 dB (96 dB theoretical, but linearity tends to degrade at
the low end of the range); if there's a 50 dB over S9 signal in the
passband and it's set to 78 dB on the green bar, we can decode signals
28 dB below S9. At 5 dB/S-unit, that's between S3 and S4. If the
strongest signal is 40 dB over S9, we can almost get down to S1.
This doesn't matter, of course, if your noise level is S8, but it
matters a LOT if it's a lot lower.
73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
