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.
Sam N9FUT
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of donroden@hiwaay.net
Sent: Monday, December 06, 2010 9:15 AM
To: amps@contesting.com
Subject: Re: [Amps] Trying to locate amplifier
I have a high band ( 150 ) GE cabinet with a single cavity 4CX250B for $200.
Don W4DNR
Quoting "Fuqua, Bill L" <wlfuqu00@uky.edu>:
> 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.
>
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|