|[AMRadio] Modulator feedback|
rickbras at airmail.net
Fri Mar 17 20:58:43 EST 2006
Thanks Don. I used a 100 uf capacitor at 160 vdc, so it should be
sufficient. I hooked it up exactly as you stated, positive to ground
and the negative lead toward the center tap of the HV transformer. I
wish I could say it stopped it, but I still have problems. It did stop
a lot of the talk back, but the feed back is still there albeit not
nearly as prevalent since I switched the 2A3 driver tubes. I made a
couple of modifications to the dynamic microphone input to better
accommodate the non amplified D-104, but I can't see how that would have
anything to do with it. I can move the mic several feet away (it has a
long cord - possibly too long) and turn the audio up enough to get 100%
modulation on the scope. The 614 has a pretty high output and it takes
little to overdrive the modulator.
Donald Chester wrote:
> How much capacitance did you use? It should be at least 20 mfd. A
> cheap electrolytic should do ok, since there is only a few volts
> across it. Put it between the midtap of the plate transformer and
> ground. The positive side should go to ground, and the negative side
> to the transformer. In all the BC-610E's I have ever seen, that
> capacitor eliminates 95% of the chatter.
> Don k4kyv
> This message was typed using the DVORAK keyboard layout. Try it -
> you'll like it.
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