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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