Unfortunately, this is a problem with crystal filters. The
filter slopes are never that equal. That's the reason Collins
developed the mechanical filter. It has equal slopes on
both sides of the passband. Something we have to live
with. de KL7HF
----------
> From: Peter A. Klein <pklein@seattleu.edu>
> To: tentec@contesting.com
> Subject: [TenTec] OMNI VI USB/LSB BFO's
To: <tentec@contesting.com>
> Date: Monday, January 19, 1998 1:15 AM
>
>
> Clark sez:
>
> >Here's my question/problem: I listen to a dead band, switch from
> >LSB to USB. The hiss sounds a lot different (shouldn't?) with the
> >PBT centered. OK, I align the PBT, it was already right, dead on.
> >It is the same. OK, I try to offset the PBT just a bit to make USB
> >and LSB sound the same as I switch back and forth. It happens a
> >little to the right of the center, but it is never really the same
> >sound. LSB had much more "depth" of lows and USB had more "highs"
> >no matter what I do.
>
> I had a similar experience. I think that perhaps the combined filter
> passband is not symetrical. The skirts seem steeper on one side than the
> other. Probably the lows go through the gentler skirt on LSB, and
through
> the steeper skirt on USB.
>
> It's not that big a deal, but you're right, it is noticeable. After
> checking the PBT alignment and finding it was correct, I decided the
issue
> was one of those famous real-world design compromises. So I decided not
> to mess with it.
>
> 73,
> Peter - KD7MW
> ---
> Peter A. Klein (pklein@seattleu.edu) : -----==3== --- ---
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>
>
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