Joe,
Just a comment here. I use FT8 frequently and almost always on 2 meters. My
interest is in weak signals. I use a Omni VII here, with a transverter. I
have had some luck using my notch filter on very weak FT8signals. Setting the
notch width at about 75hz, I have been using the edge of the filter to enhance
the signals I am looking for. So, the notch is not directly on the desired
signal, but set a few hundred hertz from it, usuallybelow it. Of course,
placing the notch directly on the signal would erase it, but I don't use it
that way. I have worked a number of stations this way. It took some playing
around to get this to work, and it does not alwayswork, and one must see the
signal first and have a decode failure, before turning to this remedy.
Just my two cents.
Best of luck,73,Andy, ka2uqw
On Saturday, December 9, 2023 at 10:05:26 PM EST, w0fy--- via wsjt-devel
<[email protected]> wrote:
Been wondering how WSJT-X generates the noise power estimate it uses to
calculate SNR for each FT8 signal. Does it simply collect all the signals and
noise over the bandwidth selected on the waterfall and call that the noise
power level or does it take a quick snapshot of the background noise level
during the brief quiet period at the end of each 15 second FT8 sequence? Or is
it more complicated than that?
I am plagued with a S2 -S3 noise level on 6 meters nearly all the time that if
not AWGN is pretty close to it. 10 meters is even worse. The DSP noise blanker
in my TS590 will reduce it slightly. I estimate this is degrading my ability to
decode FT8 signals on 6 by nearly 20 dB compared to the noise level generated
by a 50 ohm resistor. I don’t use an LNA ahead of the radio – would be
pointless. I don’t use the noise reduction feature in the radio either as it
tends to lose very weak signals completely.
Wondering if I can use the DSP in my TS590 to narrow the receiver bandwidth to
perhaps 300 -500 Hz around a known offset to help pick weak signals out of the
noise? I realize that the WSJT program filters the audio into much narrower BW
bins so all the receiver filtering can do is reduce the receiver gain reduction
caused by the noise pumping up the AGC but that might be beneficial. Likewise,
would using the DSP notch to suppress a single strong local signal or birdie
help since strong signals also reduce receiver gain? Should I deselect the
flatness option if I use these tools? Would narrowing the waterfall span help
any since the program ignores anything outside that span? Would appreciate any
insight you can share.
Joe W0FY
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