Those amplifiers used 2 of the 8560A which is basically a conduction cooled
4CX250B. The lowband versions were rated at 330 watts output and the highband
versions were rated usually at 250 watts output although a few were rated at
300 watts output. There were a relatively few amplifiers made with a single
8560A. The amplifiers had huge heat sinks and most did not have a fan/blower.
The tubes were mounted to ceramic blocks which were then mounted to the heat
sink.
If I remember correctly, those were in the highband MPB and MPY stations (i.e.
B93MMPB-3100A) and in the lowband LPB stations (i.e. B91LPB-3100A).
The MPY repeater version was very popular with mobile telephone and RCC
operations.
Glen, K9STH
Website: http://k9sth.com
--- On Mon, 12/6/10, Sam Carpenter <sam@owenscommunication.com> wrote:
Moto did make some very robust VHF tube amps. Most that I have seen come
through the shop over the years have been with a Moto marked conduction cooled
tubes that strap to a very large heat sink in the back. The tubes looked like
8873 series tubes. The tank was VERY robust and I have seen people use the RF
deck with 8877 tubes. I think these were quarter K amplifiers but would do much
more. I will look around the service manual archives we have in the shop and
see if I can find models and spec's for you. There were also tube HF amps made.
I think they were rated at a K. Power supply would not do too much more. There
is a bit of data on the web if you google around. I think I found things using
Motorola HF amplifier. I think that is where I saw the conversions as well.
There are tons of paging transmitters sitting idle right now. When I go out to
high profile sites they are just sitting there unplugged. I think the market
fell out so fast that they never picked them up or hauled any away. I think
most of the site owners would gladly have someone haul them away. Most of the
tube units were back-up for the newer glenayre solid state units. They are
pretty sweet too. I think though that the VHF amps were run in Class C. I think
that the HF amplifier started with the letters THD, or THE. That may help
refine the search. I will save this and let you know if I run across anything.
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