The tubes are definitely not triodes! The 8560A is basically a 4CX250B that is
conduction cooled rather than forced air.
Glen, K9STH
Website: http://k9sth.com
--- On Tue, 12/7/10, Sam Carpenter <sam@owenscommunication.com> wrote:
> From: Sam Carpenter <sam@owenscommunication.com>
> Subject: RE: [Amps] Trying to locate amplifier
> To: "'Glen Zook'" <gzook@yahoo.com>, donroden@hiwaay.net, amps@contesting.com
> Date: Tuesday, December 7, 2010, 12:54 PM
> I have seen these come through. I had
> always assumed that the tubes were
> basically 8873 but the size was like the 250. I think there
> may be a VHF
> that had been used for Mobile Phone service at a site
> across town. You have
> renewed my interest. I may have to drive over and look.
>
> N9FUT
> -----Original Message-----
> From: Glen Zook [mailto:gzook@yahoo.com]
> Sent: Tuesday, December 07, 2010 11:14 AM
> To: donroden@hiwaay.net;
> amps@contesting.com;
> Sam Carpenter
> Subject: Re: [Amps] Trying to locate amplifier
>
> 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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