On Fri, 2007-04-20 at 17:03 -0400, John Huffman wrote:
> I have a new-to-me Omni VI+. I have a question concerning pass band tuning
> and the filters.
>
> My Omni VI+ has these filters:
> 9MHZ
> (48058) 9429 8-pole -2.4 khz
> N1
> (48058) 9918 8-pole -2.4 hz
> N2
> 219 (48055) 6-pole -250 hz
>
> 6.3 MHZ
> 282 (49054) 6-pole -250 hz-
> 285 (48053) 6-pole -500 hz-
> 288 (48075) 8-pole -1.8 khz-
> Standard - 2.4 khz
>
> I view my audio output using Spectrogram (wonderful for zero beating for
> those of us with
> a tin ear). Using Spectrogram you can see the range of audio frequencies
> being sent to
> the headphones and speaker.
>
> When I turn the PBT knob, I can see the passband shift up or down for each
> filter except
> the 219 (48055) 6-pole -250 hz in position N2. That filter doesn't move.
>
> If the knob on the PBT is centered it shows passing a narrow band of
> frequencies (although
> not as cleanly as the other filters). If I turn the knob fully CCW there is
> no change in
> the frequencies or width. If I turn the knob CW, the audio fades and
> disappears as The
> knob is turned.
>
> Is this normal? The filter in the N1 position behaves as expected.
John,
I believe that the PBT control only affects the 6.3 MHz filters. The 9
MHz filters don't move. Make sure that when you are testing the N1
filter, you aren't seeing the effect of adjusting the 6.3 MHz filter.
Both IFs will affect the audio. This is why TenTec offers 9 MHz filters
with the same bandwidth but different center frequencies.
73,
Mark
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