[Motorola] Motorola Tube Amps

[Glen Zook]

Motorola definitely made a number of the "single
ended" 8560A conduction cooled amplifiers.  These were
used in a number of the "upright" base station 100
watt continuous duty rated units from the late 1960s
well into the 1970s.  They were especially popular in
the 60 to 110 watt output highband repeaters that were
used on RCC (Radio Common Carrier) and IMTS / MTS
(Improved Mobile Telephone System / Mobile Telephone
System).

The 8072 is identical to the 8122 electrically.  The
8072 is rated at 75 watts plate dissipation (without
external heat sinking) and the 8122 is rated at 400
watts plate dissipation air cooled.  The cavity that
Motorola used in the 450 MHz base stations and
repeaters helped with the heat sinking and thus
increased the power handling capabilities of this
particular tube.

General Electric used a lot of air-cooled high band
amplifiers using both singe and dual 4CX250 and 4CX300
series tubes.  However, Motorola used very few air
cooled tubes in their upright base stations.  One
notable exception to this was the amplifier used in
the C74BBB, L74BBB, and J74BBB 100 watt (really a
beautiful 90 watt output 450 MHz base station - you
could load them to 100 watts, wait a minute or two,
and they would almost always fold back to 90 watts,
retune, and the same thing!)series which used a single
4CX250B.  Also, Motorola sometimes agumented the air
flow in the old "quarter-K" lowband and highband units
(of which the later versions used the 4-125 / 6155
tubes) with a blower system.

Now, Motorola used all sorts of tubes that were
"cooled" only by the heatsink (thus were a combination
of conduction cooling and convection) like the 5894
and 8643 in various versions of the Motrac and Compa
base stations.  But these are not the tube types in
question.  As for "convection" cooled tubes, Motorola
used all sorts of them from the very early days!  In
fact, up until the Motrac (the driver tubes in all of
the Motrac were convection cooled and the exciter
tubes in the HHT series were convection cooled) series
all of the "normal" transmitters used convection
cooling!  In a few applications, convection cooling
was supplemented with some sort of fan to move more
air.

Glen, K9STH


--- Mike Clarson <mclarson@rcc.com> wrote:

I do not recall a one tube version of these using the
convection cooled tube--only air cooled. I do recall
the 8072 one tube version for 450 MHz. The basic
design of these 2 tube decks were quite similar thru
the MICOR era. I have some info on the MICOR amps in
30-50 MHz range, so if you do not get a response for
you exact amps, this may help.

=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco


	
		
__________________________________
Do you Yahoo!?
Yahoo! Photos: High-quality 4x6 digital prints for 25�
http://photos.yahoo.com/ph/print_splash