RCA BTF-20E

Does any one need any parts for one? Long time reader and commenter John has one that looks to be in good shape that he is willing to part with or part out.  I had three of these units in Harrisburg and my recollection is they were pretty solid units.  When tuned properly, they were low noise and sounded good on the air.

The one issue I had was with the small 100 pf pass through/by pass capacitors in the IPA.  Several went bad and were no longer functioning as bypass caps.  The result was the transmitter would self oscillate.  I think there were seven or eight of them and I replaced them all at once.  The exact model of that particular transmitter was a BTF-20ES1, which was one of the last FM transmitters off of the factory floor before the broadcast division went under.

RCA BTF-20E FM transmitter
Late model RCA BTF-20E FM transmitter

John says:

If anyone needs parts out there, I will probably cannibalize this unit as I have just too many. The separate power supply is inside the garage along with the latest version of the harmonic filter entirely made of copper.

I don’t know if the entire unit actually runs or if it is parts only.  It certainly looks like a clean unit.  As I recall, Comark bought out all the RCA broadcast parts and service. Comark was then sold to Thomcast, which was sold to Thales which I think spun off it’s transmitter division to Grass Valley Group.  Grass Valley started by making TV master control switchers, routers and other video equipment.

Anyway, if you are looking for RCA parts for FM transmitters, contact me, I’ll put you in touch with John.

16 thoughts on “RCA BTF-20E”

  1. Unit was operational when removed but had flat 4CX15000 PA tube. Very clean for its age. Well Maintained from one of my old employers. It had to go to make room for new 20 kW H-D rig.

  2. I need the following parts to quote me urgently!!

    4 socket /4CX250B
    4 contact assembly part of L113
    2 coil only with leads parte de T5
    2 CAPACITOR CERAMIC C120 500MMF 30,000V

  3. This are all the parts I need :

    4 socket 7203/4CX250B 243469

    4 contact assembly part of 1L113 232298

    2 coil only with leads parte de 1T5 231817

    2 CAPACITOR CERAMIC C120 500MMF 30,000V 076488

    6 sliding adjustment part IL 113 232298
    2 coil (bobina) IL 103
    2 capacitor cerámica 500 mmf 30 000 volts
    2 resistencias wire Wanda 6 300 ohms part 019688

  4. HI! MR PAUL THURST,I AM TECNICIAL,I WORK FOR TV STATION CH 11 CHAMPASAK PROVINCE,LAOS ,
    WE USE THOMCAST TRANSMITTER:
    POWER AMP 2000 KW,TOWER 120 M,
    START FROM 2000 (11 YEARS).
    NOW,WE HAVE PROBLEM WITH TRANSMITTER
    POWER AMP ONLY 11 ./.
    EXITER (CONVERTER) LOW MODIFY (NO SPARE PART) AND IN LAOS HAVE NOT SHOPING MARKET

    WE HAVE TO USE ITS AND WANT TO REPAIR,WHAT CAN IN DO ? HELP ME SUGGESTION PLEASE!

  5. Hello folks. I am wondering if there is any one out there who knows where I might get hold of a reject 4CX-35000-C power tube. I just want one for display purposes. Many thanks in advance for any assistance. 73. VK4BGB. Brisbane .Australia.

  6. I was looking at the picture and it reminded me of working on those transmitters in the 70’s. 7100 volts at 4 amps of plate current and they talk. I can tell you anything about it. I had a set of 20Es combined when I worked in Ohio

  7. I am not sure, I know the ES1 was the last model and had a different exciter made by Moseley. It was in the same chassis as the PCL 505 transmitter.

  8. Had two of these running in parallel at WMC FM 100 (99.7 MHz) that gave around 36 KW. That by the time it went out the circular polarized antenna gave us 300KW erp of power. Great box the fun part was keeping the power coupler balance as the tubes would age. I remember the mica flat caps in the PA tube socket that would take the screen voltage directly to ground sounding like a shotgun going off.

  9. Looking for finger stock assemblies for tuning sliders for a RCA BTF-5b. If I can’t find the parts or something that will work, this transmitter is done for. Really hate to see that happen.

  10. Have one of these in the Kansas City area. It has been sitting for many years. I’ve removed the original BTE-15 exciter for use as a backup stereo gen, elsewhere. There are many parts on a back shelf at the site.

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