Fascinating!
I am here out in the shack with the radios, and have performed the test you
outlined.
I tuned the 706 with a pick up lead to 9.000.040 to hear the Omni BFO, It
was not heard with the 706 in USB but was heard in CW mode. I then tuned
in a 400 hz note. I verified this by using the VI+ sidetone, matching the
tones exactly. Omni is in LSB with dummy load. When I put it in tune, the
tone raised, to 460 hz, again measured using the sidetone in the Omni VI+
(not the VI). The sidetone varies in 10 Hz steps.
I also have a tuner in my iPhone for tuning up band instruments which shows
the pitch of tones in notes and in Hz. The tone was 401 in LSB and in tune
466 Hz. I tried repeatedly to set the 706 to exactly 400 Hz tone, before
realizing that the 706 tunes in 10 Hz steps, so it was either 402 Hz or 392
Hz!
The sidetone setting on the VI is 700 Hz.
This was so much fun I put the top back on the VI and took the top off the
VI+, same set up other wise. The tone beat to 400Hz was much lower in
frequency, 8999.700 on the 706 to get a 400 Hz tone. When I went to tune,
the tone jumped to 768 Hz on the instrument tuner.
The sidetone setting on the VI+ is 700 Hz also.
So on the VI, the tone increased ~60 Hz. On the VI+ the tone increased 368
Hz.
This seems to confirm your "guess," Steve.
What do we do next?
Many thanks BTW.
73 de W6OGC Jim Allen
On Wed, Jul 30, 2014 at 1:01 PM, Steve Hunt <steve@karinya.net> wrote:
> Jim,
>
> Try this simple experiment if you have a receiver that will cover 9MHz:
>
> 1) Take the top cover off the Omni (4 screws)
> 2) Place a piece of hook-up wire into the receiver's antenna socket and
> drape the other end near the Omni BFO board (at rear left on the omni).
> Don't short anything!!!
> 3) Set the Omni to LSB
> 4) Tune in the BFO signal at 9MHz on the receiver. Use USB on the receiver
> and tune for a fairly low audio note - say 400Hz.
> 5) Switch the Omni to USB temporarily to check that you are listening to
> its BFO and not some extraneous signal. The audio should disappear or move
> to a very high pitch (about 3kHz)
> 6) Switch the Omni back to LSB and hear the 400Hz note again
> 5) Now hit Tune on the Omni
>
> If all is well, the audio pitch should increase to about 1kHz. I'm
> guessing with your fault it will hardly change pitch at all.
>
> Steve G3TXQ
>
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