[TenTec] Tone(s) on Pegasus receive

[Duane Grotophorst]

Yes these tones are present, I see (and hear) them in
both of my Peg’s, no discernable different between the
two radios. I’m told that they exist in Jupiter’s too.
Interestingly though I have never found them in the
RX-320, at least any that are above the noise floor. I
have also been wondering about the RX-340 and the
RX-350, is there anyone with one or both of those
radios who wants to check it out and then comment? I
am also curious about the 526? All you need to see
those tones is one of the audio processing programs,
actually most PSK31 programs would likely do. Just
fire up the program with the antenna connected to a
dummy load (or simply just disconnected), then look
for the really narrow faint lines to scroll down the
waterfall.

What you will also find about those tones is that
there is always one right smack in the middle of
whatever filter you have selected. Then there is a
second tone that will step across the filter pass band
as you tune in frequency steps that match the tuning
step size you are using. My relative measurements here
have put them at 10 – 20 dB above the noise floor of
the RX pass band. This is a real shame for an RX that
is otherwise really quiet and has minimal filter pass
band ripple. But I also have to believe though that
the problem would correctable if it is given the
attention it is due.

“If I tune to a 2.5 kHz multiple and the tone is
present, then tune 1 Hz away to get the beating tones
and then tune back to the 2.5 kHz when the beat tones
are at a null period, I can end up with the tone
greatly reduced or eliminated.”
Interesting, I had never tried this before today, I
was able to reduce the tone in the middle of filter
pass band by 5dB or so. I also think your observations
about the 2.5 KHz is correct, these tones I suspect
are an artifact of the somewhat peculiar tuning scheme
used in the Pegasus. The only operational wart that I
can really attribute to the tuning scheme is these
tones.

“Has anyone else noticed this or is this problem
unique to my Pegasus, indicating that something is out
of alignment?”
I doubt if it is out of alignment. It is also strictly
in the firmware, the control program has no bearing at
all on it. It is one of the first things I look at
whenever a new firmware version comes out.

“Or is this just a case of me being too critical in my
analysis?”
I would say not, this issue is really no less
important than smooth QSK operation is for example.
For most day to day SSB, CW, and PSK31 (or SSTV?) work
they will not too likely be noticeable, however what
I’m finding with WSJT meteor scatter software is that
they are proving to be troublesome. WSJT will
frequently interpet one of those tones as being one of
its 4 tones that it is looking for in the meteor
pings. I have not yet tried working with JT43 (a PUA43
variant) but I am afraid that those tones will make
the Pegasus unusable, JT43 is designed to work with
signals ~20dB BELOW the noise, needless to say a spurs
40dB higher will be a problem. And as Larry, VA3LK has
pointed out in his response this problem is not
totally unique to the Pegasus/Jupiter, I found tones
and other obnoxious stuff in some the other radios I
have here, and many of those rigs have significant
pass band ripple as well.

73,
Duane
N9DG

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