On Sat, 2009-03-28 at 15:06 -0400, yash@aol.com wrote:
> Jerry
> ?the bpt seems to work as it should,varies the signal as it should ,except
> the signal STARTS off as the poor audio signal. I did notice the BPF and the
> fade controls do next to nothing for the audio the fade is ok ,but the BFP
> does nothing.... I noticed the BFP does cut the audio width from 200 to 1700
> while it is in use, per the manual.? possible the circuit is not dropping out
> somehow? this seems to me the 200 to 1700? would have the no bass, tinny
> sound I am hearing. Ive never had a rig with a BFP before ,maybe my
> understanding of its use is not correct?
> dale wt4t
>
>
>
>
>
The effect of the bandpass tuning depends on what filters are in use at
9 and 6.3 MHz. If the filters are of comparable bandwidths, moving band
pass tuning off of zero narrows the receiver bandwidth. One filter sets
the high side, the other filter sets the low side. Practice on a carrier
to see the effects, tuning past the carrier as a manual spectrum
analyzer (though a computer sound card based audio spectrum analyzer
works with noise a the signal source just fine, even a PSK-31 waterfall
works for that).
If the 6.3 filter is narrower than the 9 MHz filter then it will set the
receiver bandpass and one that is moved over the spectrum passed by the
9 MHz filter until it gets to the edges. Then depending on the direction
of offset one filter sets the high side and the other sets the low side.
Again a manual sweep past a carrier or a computer audio spectrum
analyzer can be very handy tools towards visualization of the results.
73, Jerry, K0CQ
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