Makes sense, Brett. I was trying to work it through using diodes at the
"bottom" of the grid-leak resistor, and there didn't seem to be a simple
solution that way. But since I'm using the grid-leak resistor also as
the RF choke (typical old-buzzard practice), so I'd have to add an RF
choke. May play with that at some point...
73,
-Larry/NE1S
Brett gazdzinski wrote:
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
biased.
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.
Brett
N2DTS
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] 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)
Sorry!!!
That was supposed to read "Could you or DON describe the
protective bias
circuit you refer to? "
-'1S
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
