|[AMRadio] Re: 1930's Old Buzzard Open Rack Transmitter Finally
brett.gazdzinski at verizonbusiness.com
Thu Feb 23 19:19:47 EST 2006
The grid gets its bias the normal grid leak way.
At the grid side of the resistor, a diode is installed between the
bias supply and the grid, in the direction that allows it to pass
bias, but if the grid leak exceeds the fixed bias, it is reverse
That's cathode towards the bias supply I think.
I like using big panel mount pots for grid leak, I have some BIG ones
I got at fests for a buck each, 75 watt jobs of different resistances.
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of ne1s
> Sent: Thursday, February 23, 2006 4:42 PM
> To: Discussion of AM Radio
> Subject: [AMRadio] Re: 1930's Old Buzzard Open Rack
> Transmitter Finally SeestheAirwaves! (Long)
> That was supposed to read "Could you or DON describe the
> protective bias
> circuit you refer to? "
> ne1s writes:
> > Thanks for the kudos, John!
> > Could you or done describe the protective bias circuit you
> refer to?
> > Probably could figure it out, but the group may be
> interested as well...
> > 73,
> > -Larry/NE1S
> > John E. Coleman (ARS WA5BXO) writes:
> >> CONGRADULATIONS A JOB WELL DONE!
> >> I really like the choice of tubes. I don't know what a
> T55 is but
> >> probably one of the special Taylor triodes with 55 watts plate
> >> dissipation.
> >> Probably not a lot different than the 812s but I know that
> the 812s are
> >> very
> >> good tubes to use in a class C plate modulated rig
> especially if used
> >> with
> >> 100% grid leak bias or the configuration that Don, K4KYV,
> uses where
> >> there
> >> is a safety bias supplied thru a diode and the diode
> becomes reversed
> >> biased
> >> when RF drive causes grid leak bias. The 100% Grid leak
> bias DOES make a
> >> difference in the modulation characteristics of the rig.
> >> John, WA5BXO
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