[R-390] unstable BFO note on R-390A

[Dan Merz]

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Bob Young
Sent: Saturday, December 16, 2006 2:18 PM
To: r-390 at mailman.qth.net
Subject: RE: [R-390] unstable BFO note on R-390A

Dan,

"Thanks, but the problem is that there is a flat part on the shaft where the
set screw goes which only allows a little leeway either way for the knob."

I forgot about the flat on the shaft which means you have to make the
adjustment I mentioned using the coupling between the shaft sticking out the
front panel and the shaft going into the i.f. chassis,  by disconnecting
this coupling behind the panel,  adjusting the bfo frequency with the shaft
going into the i.f. chassis and then reconnecting with the knob pointing at
zero.    But it sounds like you have a problem with the main tuning so this
adjustment should probably only be done after you clear up the main tuning
problem if that's the cause of what you're experiencing.  You need an
independent way of monitoring the bfo frequency to see if it's actually
changing or whether the change in beat note frequency is due to change in
the main pto jumping around in frequency.  I seem to recall that I used a
signal generator to see what my center i.f. frequency was and then I set the
output of the bfo to that using a frequency meter and then connected the
front shaft with the bfo producing that frequency.  Without the signal
generator/freq meter,  zero beating the noise is about as good a method to
get the bfo at the right frequency before tightening the clamp between the
two shafts behind the panel. Dan.  

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