I've been working with my Pegasus and have discovered that when I am in CW
mode with a narrow filter (300 Hz) and no input signal (i.e. connected to a
dummy load) and tuned to a multiple of 2.5 kHz (I've tried several) that
there is a steady tone audible and noticeable on software that monitors the
audio input, such as the waterfall display on DigiPan. The tone is exactly
at the frequency of the CW spot tone, but the spot tone is turned off. I
have my CW offset (and thus, spot tone) set to 600 Hz (the same as on my
Omni V).
If I tune slightly away from that frequency, it becomes apparent that there
are actually two tones involved. Being 1 Hz away from the 2.5 kHz multiple,
the tones actually beat against each other and the level of the perceived
tone fluctuates at 1 Hz. As I move further away, the tones can actually be
seen to separate on the waterfall display.
I have also found that by careful manipulation of the tuning, I can reduce
or eliminate the tone. 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.
Note that the level of this tone is usually much less than the normal
background noise with an antenna connected, but if you examine the waterfall
display with the antenna connected, the tone is still there.
I believe that the 2.5 kHz spacing is relevant as that is the frequency
steps used by the first local oscillator in the Pegasus mixing scheme.
I've been able to verify this condition using both the TT supplied software
and N4PY's control program.
Has anyone else noticed this or is this problem unique to my Pegasus,
indicating that something is out of alignment? Or is this just a case of me
being too critical in my analysis?
Comments?
73,
Mark, N8ME
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