[Amps] Trying to locate amplifier

[Glen Zook]

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 at 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.