Perhaps it was a GE.
I can't remember if it has two big dials or just one. One control went to the
swinging link coupling.
But it did have a pair of forced air cooled bypassed EF Johnson sockets for
either 4x150 or 4cx250 tubes.
73
bill wa4lav
________________________________________
From: Glen Zook [gzook@yahoo.com]
Sent: Sunday, December 05, 2010 11:21 AM
To: Amps@contesting.com; Fuqua, Bill L
Subject: Re: [Amps] Trying to locate amplifier
Motorola may have built such an amplifier for the military. However, for the
commercial FM two-way market the Motorola lowband and highband amplifiers used
8650A tubes which are the conduction cooled versions of the 4CX250B. General
Electric made thousands of lowband and highband amplifiers using the 4CX250B
that had dials similar to those made by National.
Motorola did make a 450 MHz amplifier using a single 4CX250B rated at 100 watts
output. However, with the power supply that Motorola used, plus "something" in
the actual physical construction, when tuned for 100 watts output the amplifier
would make that for less than a minute and then drop back to a steady around 90
watts output. I have one of those amplifiers that I tuned down to 432 MHz
(tune down without any problems) and bypassed the external bandpass filter.
Without the filter (the amplifier is still "clean") it makes about 150 watts
output on CW. I haven't used the amplifier for a while but need to redo the
bias so that I can use it for SSB as well as CW. The original design is Class
C for FM operation.
Glen, K9STH
Website: http://k9sth.com
--- On Sun, 12/5/10, Fuqua, Bill L <wlfuqu00@uky.edu> wrote:
Many years ago (late 60's) I converted an amplifier which was a low band VHF to
20 and 15 meters. It had a pair of push pull 4CX250B or perhaps 4X150A tubes
(no tube came with it). I parallel connected the tubes, both halfs of the plate
capacitor and used the whole coil. I also use a dual 365pf variable to convert
it to a PI network. I first used it for a while with 4X150s until I came across
some cheap 4CX250B's.
In any case I am looking for another one. It had some vernier dials National on
the front as well. Does anyone have an idea what this was? I believe it was
made for the military by Motorola.
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