[R-390] Filter Bandwidth Question

[Dan Merz]

Hi, yes those two positions, 1 and .1, use the crystal filter. L503 should be adjusted so they have the same center frequency. I don’t recall, or have ever known, whether the two positions attenuate a narrow signal the same. I would guess the .1 position would attenuate a broad signal more than the 1 position by definition.  The alignment procedure on the crystal neutralizing capacitor and L503 is such to make the .1 position symmetrical and the 1 peak centered on the .1 peak.  Dan 

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> On May 11, 2020, at 2:06 PM, Bob Young <bobyoung53 at hotmail.com> wrote:
> 
> I'm pretty sure that at least the .1 position is crystal, I think the 1 khz position is too, aren't there only four mechanical filters in those? I have a Capeheart too, nice radio.
> 
> Bob Young
> kb1okl
> 
> ________________________________
> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Ed G <ed.n3cw at gmail.com>
> Sent: Monday, May 11, 2020 4:59 PM
> To: r-390 at mailman.qth.net <r-390 at mailman.qth.net>
> Subject: [R-390] Filter Bandwidth Question
> 
> Hi Folks,
>     My Capehart 390A is working mostly FB, but I do notice what would appear to be filter loss when I switch down to the .1 filter bandwidth.  All other filter positions seem to be fine with no difference in signal/S-meter readings when going from 16 KC down to 1 KC.  But when I go to .1 KC signal level does drop down noticeably. I thought the 1 and .1 positions used the same mechanical filter, so perhaps the problem is something else (load resistor)?  Any suggestions on what to check?  Thanks!
> --Ed—
> 
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