I think this is a result of 2 AM broadcast stations mixing (intermod) with
the resultant spur ending up on 1.818. I dealt with a very similar peoblem a
few years ago from an errant ham who accused me and our station of causing
the interference. He even called the FCC and reported our station as the
culprit, even though I knew we were not at fault. I did the math and figured
out who was causing the problem but by that time the FCC had been notified
and made the measurements and called me to acknowledge that we were not at
fault. The ham who reported me called back a week later and said he had
wanted to let me know that he figured out we were not the problem. (tried to
make up for his shoot from the him diagnosis) Just for anyones info he (Tom)
is a regular on the 160 meter Top Band Reflector. He was very lucky he was
not litigated against by our corperation ( that was considered) but never
called back to admit error.
----- Original Message -----
From: "Duane Grotophorst" <n9dg@yahoo.com>
To: "Mark Erbaugh" <mark@microenh.com>; "Tentec (E-mail)"
<tentec@contesting.com>
Sent: Saturday, December 14, 2002 1:00 AM
Subject: Re: [TenTec] Spurious Signal on Pegasus
> Mark,
>
> What I think you are seeing is an image response of
> the 12KHz (nominal) 3rd IF. As you may recall there is
> a 467KHz LO3 signal being mixed with the 455KHz 2nd IF
> signal to arrive at the final 12KHz (+/- 1250Hz) 3rd
> IF.
>
> I think you would have also found another at 1.8125 if
> that frequency was otherwise quiet. If you can inject
> a locally generated strong signal into the RX does the
> offset of these "images" vary between 5.375 and 6.625
> KHz away by chance depending on the actual frequency
> of the main (desired) signal? If so then I would
> believe that there is also an interaction between
> LO1's 2.5Khz tuning step size and LO4 - which is
> mathematically manipulated (tuned) inside the DSP
> algorithms.
>
> 73,
> Duane
> N9DG
>
> --- Mark Erbaugh <mark@microenh.com> wrote:
> > Tonight, I was tuning around 160 with my Pegasus. I
> > heard W1AW very loud, clear and steady on 1.818, but
> > I also heard them with a weak a fluttery (I could
> > see the audio frequency wavering on my waterfall
> > display) at 1.8235. I tried to copy them with
> > another radio, but no luck, so I am assuming that
> > this was a spur inside the Pegasus. Any idea what
> > causes it?
> >
> > 73,
> > Mark
> >
>
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