[AMRadio] info wanted on 4-400 linear amplifier

John Coleman ARS WA5BXO wa5bxo2005 at pctechref.com
Wed Aug 3 10:09:22 EDT 2005

Grid driven linear amps are a challenge sometimes even tetrode tubes
need to be neutralized.  Neutralization not only prevents spurious
oscillations but it also stops phase modulation products.  Swamping the
grid circuit with a dummy load is a good idea because it reduces the 90
degree feedback that we are trying  to neutralize and makes the driver
radio a lot happier with a more constant load.  The nice thing about
grid driven is it would be easy later on to plate modulate and run it
class C.  As for linear amps I thing GG is a better solution especially
with triode tubes made for the purpose.

You may want to join in the mail group called AMPS CONSTESTING lots of
really smart guys their on linear amps.  


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of zuu6k at juno.com
Sent: Tuesday, August 02, 2005 8:10 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] info wanted on 4-400 linear amplifier

I am planning to build a linear amp around a grid driven 4-400 tube. Can
anyone suggest where I can find a suitable circuit with component
I would like band-switching for 80, 40 and 20 meters. I will be driving
it with a 25 watt carrier output rice box on AM. I don't like the one in
the ARRL 1967 handbook because it requires you to open the lid and
physically change taps on the coil and change tuning capacitors. I don't
have any other older handbooks. Thank you.

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