Date: Wed, 15 Aug 2012 20:23:24 -0400
From: Bill Fuqua <wlfuqu00@uky.edu>
Subject: Re: [Amps] Schematics ??for 4CX250B GG HF amplifier
Every once in a while we revisit this topic.
I will just cut and paste the following from some time ago.
Bill Orr's article about super cathode driven tube amps
in the July 67 QST.
He has a example of a 4CX300A (control grid connected to cathode) cathode
driven amplifier.
It only has a power gain of 5. 375 watts out with 75 watts input. But the
nice thing is that the 3rd order products
were 46db down and 5th were -49. This is quite an improvement over most
amplifiers.
I have always wanted to do this using two stages one produce around
300watts output and the second 1500 watts.
A 4CX250b driving 4 parallel 4CX250B tubes. Should get similar results. This
naturally would require 50 to 70 watts drive.
73
Bill wa4lav
## several 4CX-1000 amps in super cathode config were built locally back
in the
70’s and also 80’s..with great success. Control grid strapped to cathode,
and
screen grid bonded to chassis. The entire mess was operated as a high mu
triode.
160 watts of drive for 1200 w out. 8.75 db gain. No resistor’s used
anywhere.
The 4CX-1500 can also be used in the same config. PI type tuned input
required.
## The 4CX-5000 has plenty of control grid diss. The 4x5 and 4x10 in GG
was just like any 4-1000 in GG. Both grid + screen strapped to chassis.
Then you drive it with a SB-220 in the CW position. The 4x15 has even more
control
gris diss. Same deal. PI type tuned input required.
Later.... Jim VE7RF
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