[TenTec] Passband

Ken Brown ken.d.brown at hawaiiantel.net
Tue Jul 5 21:00:58 PDT 2011

Keith Hamilton wrote:
> I hear the default 700 Hz tone thru the 500hz filter with the band pass control centered. When I switch to the 250 Hz filter the tone remains 700 Hz  The signal strength goes to almost 0. To bring the signal strength back, I must tune up the band raising the tone heard at the same time to an unacceptably high level  This should not happen if the passband of the two filters is the same. 
Or you could adjust the PBT while leaving everything else alone. The 
tone frequency will remain the same and you should be able to find a PBT 
setting that maximizes the amplitude of the signal producing the 700 Hz 

A firmware and hardware upgrade to the Omni VI could have a setting for 
the PBT changed by the 6.3 MHz filter selection. This would require that 
the microprocessor have control of the 15.3 MHz VCXO in the PBT system, 
which it does not have.

Another upgrade I dream about (which is just as unlikely to ever become 
a reality) is for the microprocessor to have control over the BFO 
frequency. Not just five choices, but actual control. This would allow, 
with the right firmware, an adjustable sidetone that coincides with the 
signals that pass through the 9 MHz IF filter. There would be no need to 
have "high note" and "low note" and RTTY narrow filters of all the same 
bandwidth with different center frequencies.


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