RCA BTA1M transmitter

[MacroC]

Hello all!

I'm restoring an old RCA BTA1M transmitter. It was the first transmitter of the radio station I work for and I intend to get it working again. I've searched the Internet for the circuit diagram but no joy.

Does anyone have a copy of its technical manual or just the circuit diagram? It uses 807 and 833A tubes.

Any help will be much appreciated.

Thanks in advance,

[Paul G]

Go to this link, they a RCA BTA manual listed:

http://www.americanradiohistory.com/Arc ... gs_RCA.htm

Paul...

[MacroC]

Hi Paul,

Unfortunately, it seems that BTA1M isn't listed at that site.

Models BTA1M, BTA1MX, BTA1L and BTA1R have different architectures and the circuit diagrams don't match.

Many thanks for your kind reply.

[Shane]

Is the L even a little bit similar? It seems to have a similar tube complement. Might it be enough to get it going if not an authentic restoration? Is your M closer to the L or the R in form? A station I once worked for had a 1kw RCA which I think had 833s but it was a one or two cabinet deal not 3 like the L as I recall. That station went on the air in 1957 so I'm thinking their transmitter might have been previously used before they got it rather than new, contrary to what I thought at the time.

We have a 500R that I think was commissioned in '55 so that would make your M older than that.

The R series is one cabinet at that power level and used the "new" tetrodes 4-400A, 6146, and 2E26. Had a few ham rigs with the 6146 or 2E26. But it's just me talking. You probably know all this already.

I checked oldradio.com but no luck there either.

Good luck on the search. SOMEthing has to turn up!

[MacroC]

Hello all!

Many thanks to all of you who tried to help me. Have finally found a complete manual with the correct schematics diagram.

For those who may be interested, it's at: http://bama.edebris.com/manuals/rca/bta1mx/

Click on bta1.pdf.

All the best.

Marcus
Radio Itatiaia - Brazil

[Shane]

This is great! That is the model I was thinking of and upon further deflection, there were two stations in my past that had these. I can't find a date anywhere in the manual, though. Thinkin' they must have been from the 40's.

Stations in question, should anyone be curious, were WHTG and WAEB, both of which still have the same call letters.

[Dale H. Cook]

Thinkin' they must have been from the 40's.

The M series were in production in the 1950s, as the L series were still in the 1950 RCA catalog.

[Shane]

When did they start using 4-400s, Dale?

[vacuum tube]

They started using the 4-400's in the BTA 1R1 which I believe came out in 1959 or 60.

[RodeoJack]

So... why did the industry move away from the 833 and over to the 4-400? It seemed the 833-based transmitters were better performers, especially those that were still in use as the Dorrough and CRL processors were introduced. I'm guessing the industry felt the same way, introducing the 4-500 and , for awhile, the 5-500 in the Collins 820D-2 which, IMHO, was a pretty good rig.

Thinking back on it though... I guess Gates stayed with the 833. RCA, Bauer, Collins, McMartin and most, if not all of the transmitters Bernie had his hands on moved to 4-400s.

In the early '70s it was amusing to see a 4-400 based transmitter sit next to a Frese "Audio Pilot". Opened up a bit, that processor could flatten a set of modulators fairly quickly, and contributed to the demise of at least a couple of mod transformers, as I recall. With that combination, a set of 4-400s in a rock station didn't stand much of a chance.

[RGORJANCE]

Yup! 833 's will glow red a lot longer than a 4-400.

Got an RCA BTA1MX up in Sheboygan with 833's. I think I had to replace the jugs once over many years until we put the Nautel in. It has been in standby for so many years I doubt the CE has even turned it on in about 12-13 years. It might just crater if he tried.

Fossil

[Shane]

Hm. Together with the manufacturing troubles with 4-400s you might have explained why, toward the end of our Bauer 707's service as a main, I was getting only about 8 months out of the tubes: CRL processors. They were cranked pretty hard although the large majority of programming was/is talk.

That, except for the mfg. difficulties, doesn't explain away or excuse Triton for supplying me 2 DOA brand new 4-400s in the early 2000s. I think that's been gone over here before.

Can you still get 833s?

[Dale H. Cook]

Can you still get 833s?

I haven't had to order any in years (got shut of my last Gates, a BC-1G, years ago), but we were buying the Chinese "National" brand 833C from Richardson and got good performance and life from them. Richardson still sells them but I don't know if they are still as good.

The only new tubes I have ordered in recent years have been been Greenstone http://www.greenstoneusa.com/industrial.htm - 4CX5000A for Collins 212E-1. I have been pleased with performance and life (and the owner with price, which I do not know). Support was excellent when we got a dud some years ago, and they outlast the late-model Econco rebuilds (owner says he gets more life per dollar from the Greenstones). Greenstone sells the 833A and 833C, but I do not know their origin or quality.

[Kent T]

The "National" brand 833a tubes are still very good and last well. No issues with them in a old Gates deep backup, an old BC-1F. It gets used and exercised regularly, on 800 and has been since new in 1953. We keep the processing light when we need to use it. Dual alternate main BE AM1A transmitters replaced it. That Gates is clean and in superb condition.