Hi all,
Thanks for the suggestions. Further investigation on the BPF board using
an injected receive tone:
- Switching diodes are being correctly biased when 12m is selected (and not
biased when it is not)
- Both diodes are passing signals correctly when on - verified by checking
on either side of the diode
- But the 12m filter section itself attenuates at least 25 dB from in to
out (on the inside of the diodes) - verified with a calibrated signal
generator and spectrum analyzer. This is huge compared to other bands
which pass the proper signals with little attenuation in the center of the
band.
So no choice but to unbolt the boards and rework the solder. I have
access to a full SMT rework station, but if Malcolm would like to send
suggestions to my email (check QRZ.com), that would be lovely.
Thanks all - more later.
73
Phil W1PJE
On Wed, Jan 2, 2019 at 12:51 AM Malcolm McLeman <f5vbu@cegetel.net> wrote:
> Although possibly not the answer to your problem a simple non
> test-equipment Omni VI test worth conducting regularly...
> As an almost sight-loss octogenerian who has (for the umpteenth time)
> just replaced RX signal-path switching diodes on my Omni VI BPF board
> may I suggest a simple (non test-equipment) test before delving in with
> soldering-iron.
> Remove top-half main casing and LS alu bracket at the rear then with
> headphones choose any weak signal or even backround noise check the
> difference between antenna plugged in normally and antenna direct to
> PL17 O/P (under LS bracket) to the band filter. If there's any
> perceptible increase in signal/noise strength then surgery is required
> and if that's the case don't attempt without advice which I'll happily
> provide direct via email. HNY GL et 73 Malcolm/F5VBU.
> ps Reason for my final sentence? TT PCB quality control should've been
> shot comparing their junk to contemporary radios from YIK-San or better
> still JRC.
>
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--
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Phil Erickson
phil.erickson@gmail.com
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