Reino,
I really have no data to compare as you suggest, and the results are purely
annecdotal.
The way this got started was that on 2 meters I suffer from local rfi, usually
these are suspected to be chargers in the vicinity. In engaging filters I
noticed the rfi become enhanced, by observingnearly imperceptible rfi become
completely visible. So, I wondered if I could do the same with a very weak
signal. In some cases, a non-decoding ft8 signal which is very light in color,
often becomesdarker, nearly orange at times and decodes. Using the method, I
have worked quite a few stations otherwise impossible to decode. And yes, the
signal reading reported by WSJTX will change, sometimesdramatically. As I
posted earlier, the method is not foolproof, it doesn't always work. QSB does
not help the matter, of course.
It's important to mention that I do this only on 2 meters. Often the target
signal is the only one on the waterfall so I can spend time zeroing in on it.
I can only suggest that it be tried, maybe I'm wrong, but I use the method
pretty regularly.
I have noticed the same results on Q65, but generally have not spent much time
with it there.
73,Andy, ka2uqw
On Sunday, December 10, 2023 at 11:25:32 AM EST, Reino Talarmo via
wsjt-devel <[email protected]> wrote:
Hi Andy,
Interesting approach. But how you know that it really enhanced the signal
detection?
The wanted signal is now close the wanted signal and that may disturb the S/N
calculation and you will see a better S/N values with your method without a
real better sensitivity. Possibly the only real comparison could be with two
radios fed from the same antenna with a power divider (you may need a an
amplifier before the power divider for compensating attenuation) and two
instances of wsjt-x. Then a statistical study of success/failure rates could
tell a real story.
Just my two pennies.
73, Reino OH3mA
From: Andrew Neumeier via wsjt-devel [mailto:[email protected]]
Sent: Sunday, December 10, 2023 3:40 PM
To: w0fy--- via wsjt-devel <[email protected]>
Cc: Andrew Neumeier <[email protected]>
Subject: Re: [wsjt-devel] WSJT noise estimates
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 FT8
signals. 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, usually
below 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 always
work, 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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