On Mon, 2006-11-27 at 09:14 +0000, Steve Hunt wrote:
> Ken,
>
> Gary, W7TEA, kindly sent me a photo of the underside of his early Omni VI+
> which has the screening in place. There are no holes in my "inner panel"
> which would allow screens to be attached, so this must have been a mod on
> later Omni VIs / Omni VI+s.
>
> I have put temporary screens in place but they made no difference!
>
> One final symptom on the "birdies" which totally mystifies me: If I adjust
> the PBT control until I hear a birdie, then press the NAR button, the pitch
> of the birdie changes by a few hundred Hz; pressing the NAR button again
> returns it to its original pitch. I can't see anything on the schematics that
> would suggest that the NAR button affects any of the oscillators!
>
> I think I'm just going to have to live with it.
>
> 73,
> Steve
Doesn't NAR change the filter bandwidth and then the controller adjust
the BFO frequency and the main oscillator frequencies to keep the offset
from BFO to IF filter the same and the main oscillator to compensate to
keep the received zero beat frequency the same? Then when the birdie is
created without the main oscillator, moving the BFO gets that frequency
change.
I've seen mixer products of such birdies in my Corsair II up to a few
hundred MHz. Long ago, I found some calibrator beat notes in a LM-11
frequency meter using tubes up to a couple GHz. The interesting thing is
that not all were present even though I wrote a computer program to
forecast their possibilities. Those that were present made it possible
to improve the accuracy of the frequency meter, though the frequency
counter made it totally obsolete.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|