[R-390] That R-390A "BFO Thingy"

Sun, 27 Oct 2002 09:14:47 -0800

They are ALL 1:1. They were built for multi-turn pots which were therefore
built-in verniers over the single turn variety. They all mount to the front
panel nut.

Bob
-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Barry Hauser
Sent: Saturday, October 26, 2002 10:54 PM
To: Philip Atchley; [email protected]
Subject: Re: [R-390] That R-390A "BFO Thingy"

Hi Phil & crew:

I bought a couple of those odometer style BFO knob things a while back.  As
Bob pointed out, they are not verniers -- 1:1.  The idea may have been to
improve reset-ability, but they introduce some slop.  Some may be worn
inside and the action is rough.

They are not difficult to fit, but I doubt if it will help you.  Best bet is
to find the small "combination lock" style verniers -- the ones you see on
some scopes and other test equipment, though I don't know if they use a 1/4"
or 1/8" shaft size. They usually also have a locking lever.  That would give
you vernier reduction and an accurate scale for resetting. Not sure how they
mount up.

Alternatively, there are those small inline vernier couplings which I think
are still available new from catalog sellers.  It's possible they would just
fit in without drilling, but the existing shaft might have to be shortened.
The ones I'm thinking of don't have scales, though.

Barry

> Hello all.
> I use VERY sharp audio filters with my R-390a in the CW mode.  While my
> receiver is easier tuning than 'most' I've had it can still be a little
> difficult sometimes to exactly set the tuning in the center of the Audio
> bandpass (my present sharpest filter is 80 Hz but I have a much sharper
one
> coming).  I sometimes like to tune my receiver where the desired signal
> makes it through the filter and the undesired is off the slope of the
> filter, sometimes hard to do with strong nearby carriers.
>
> I sometimes use the BFO to "tweek" the audio note a tad but then have to
> reset it back as I use the 100Hz IF filter too.  Resettability is good,
but
> could be better.
>
> Some of the 390A's I've seen have a little BFO vernier for setting the
BFO.
> Are these good and resettable (seems like they would be).  Can they be
> retrofitted to a receiver that doesn't have one or is it a pain?  And
> lastly, are they available at reasonable cost?  Can't get one right now
but
> I'd be interested in hearing what the group has to say.
>
> 73 de Phil  KO6BB

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