[BC] Re: Transmitter evolution- Comments????

[cldube]

OK- now I see that you guys are talking about a Harris transmitter!
BRRRRRR- do not pass Go, do not collect $200... Chuck.
(I just saw the other responses as listed below....)

We have a BE FM-20B. One single 4CX12000A.

Sorry about the mixup.........

Chuck Dube
WFCR


----- Original Message ----- 
From: <DHultsman5 at aol.com>
To: <broadcast at radiolists.net>
Sent: Saturday, October 22, 2005 8:17 PM
Subject: [BC] Re: Transmitter evolution- Comments????


> In a message dated 10/21/05 2:18:38 P.M. Central Daylight Time,
> miltron at mindspring.com writes:
>
> Our  FM-20B has no such thing. Was this common of earlier versions?
>>  Exciter, IPA & control board are all 220. Anything lower comes from a 
>> PS
>> (i.e. fans).
>> Once you kill the three phases, it's  cold.
>>
>> Chuck Dube
>> WFCR
>>  Amherst
>>
>
> ********************************8
>
>
>
>
> Is your FM20-B the transmitter that has two 4CX10,000 tubes?    Wow that 
> is
> an oldie. But probably a first of its type.
>
>
> #######
> Memories opened.....
>
>
> The FM20H did have dual AC feeds, all the way to the 20H3 model.  It  also
> used 110VAC control circuits even for the remote controls.  It  had a VSWR 
> meter
> but no VSWR protection, that was standard, until it became the  FM20K
> product.  The transmitter was an outgrowth of the FM-G  Series.
>
> I may have this mixed up but I am certain that someone will correct  me
> since I am certainly not an expert on Gates/Harris transmitters.   However 
> as an
> old time broadcast engineer I was aware of most of the products  used and 
> have
> used many of the one I speak about.
>
> I believe what was the  the FM**-G series transmitters, 3 kW, 5 kW.,  7.5 
> kW,
> 10 kW. and 20 kW.  all used the 4CX5000, tube to 7.5 kW.,  the  4CX10,000
> tube at 10 kW. and the 4CX15000A tube to 21.5 kW.  All of these 
> transmitters
> used  the Gates serrasoid exciter 10 Watt tube type multiplied  862 times 
> to
> frequency.  These had two versions the last being the  M-6095 "Dual 
> Cascade"
> modulator which was converted to stereo, using the  M-6164 Stereo/SCA 
> Generator
> inserted in the multiplier stage of the  exciter.
>
> The were all self contained within the same sized cabinet except in the 
> 7.5
> kW. and above had external coaxial harmonic filters and the 20 kW. had an
> external Plate supply cabinet.
>
> The FM**H series came with the development of the TE-1 solid state direct 
> FM
> Exciter, I believe the engineer was Hardin Stratman.  The FM**H3 series 
> came
> from the upgrade to the TE-3 Exciter  which was done bu Jack Sellmeyer.
> There were several  colors involved in this series of transmitters.
>
> Now regarding the FM-20B....it seems that the top power for most FM
> transmitter manufacturers was 10 kW.  Many early manufacturers just added 
> on
> amplifiers but seldom built larger than 10 kW.  RCA built several  50 kW. 
> FM
> transmitters one used here in Birmingham for WBRC-FM at 500 kW. 
> horizontal only.  They
> built several of those transmitters.  Later  they used the TV ring 
> amplifier
> for the high powers in Michigan at the  Fetzer stations. The ring 
> amplifier
> was driven by a standard 10 kW. FM  transmitter.
>
> There was little demand and FM was not a revenue generator in most cases
> until the early 1960's inspite of being on the air since late 1947.
>
> Gates and RCA both used early external combining techniques to achieve 20
> kW. using two 10 kW. final amplifiers.
>
> Collins had discontinued manufacturing of their 730* Series of FM
> transmitters as had GE and Westinghouse sometime in the early to mid 
> '50's.  Western
> Electric's FM line was sold in 1952 as part of the FTC's trust  busting. 
> I think
> Standard Electronics may have evolved from the Western  Electric 
> line??????
>
> ITA worked on a 15 kW. and a 20 kW. using two 4CX5000 or 10,000 tubes 
> within
> the same cavity.  The Gates FM20-B was similar with two tubes within  one
> cavity. I believe that this was the first single cavity 20 kW.  FM 
> transmitter.
>   COMMENTS PLEASE?????
> I am trying to recall this information as accurately as possible so your
> help is important for to be correct.
>
> Then along came the Eimac, RCA, Machlett 4CX15,000A tetrode tube which had
> the gain and dissipation to make the VHF 20 kW. with a single  tube. 
> Collins
> (back in the business with their 830 Series), Gates and  RCA all 
> immediately
> came out with new 20 kW. FM transmitters for Class C  operations.  With 
> stereo
> coming June 1, 1961 all manufacturers geared  up for new stations and new
> transmitters.  Rust, GPL, CCA, AEL,  Bauer and others entered the 
> marketplace.
>
> Eventually the triode for FM increased in power. and twenty kW. could be
> reached with three  tubes.  Usually the tube line up was a 4CX250  tetrode
> driver, a 3CX3000 or 3CX5000 IPA driving a 3CX10000 or 3CX15000.
>
> All this to respond to the Gates 20B  not having two AC feeds..   I think
> I'll take a nap.
>
> Dave Hultsman
> Back home from the SBE National Meeting
>
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