Tuesday, April 3, 2012

1947 RCA BTA-50F Catalog, From Engineer Hollis Duncan!

Hey Bud,

Here is a link to the June 1947 issue of RCA Broadcast News announcing their brand new BTA-50F AM transmitter. It has lots of nice pictures and a schematic. Best regards, Hollis


Very COOL, thank you, Hollis! There's more in this copy (from RCA Broadcast News) to enjoy, so sit back and read on!

Dear Reader and Visitor, if you remember my visit to Little Rock a year ago this month, you'll likely remember all the pictures I posted here...many of the transmitter itself. This catalog, Hollis so thoughtfully forwarded for us to enjoy, explains a LOT of the goings-on in the different stages and areas of the transmitter...so fantastic!

David B. Treadway and Jerry Sims both were my guides there at the transmitter site. I hope David B. enjoys this catalog...and I wish Jerry were alive to see it, as well....

Enjoy, compliments of Engineer Hollis Duncan!

Bud S. (staceys4@hotmail.com)


  1. HUGE thanks to Hollis for sending in this invaluable piece of history of the F Model, which appears to be the last of the all-tube RCA 50,000 watt transmitters. (From what I read, some solid state components began to be used on the G Model in the middle 1950s.)

    One characteristic of the RCA BTA-50F that I find fascinating to the point of incredulity was the reliability of its Power Amplifier and Modulator tubes. The engineers at KMPC 710 in Hollywood claimed EIGHTY THOUSAND HOURS on some of their tubes! (From the link below, you may also notice a similarity to the way one Felix McDonald kept his own transmitter facility.)


    To have worked with such a monumental machine as this has given us a glimpse of Immortality.


  2. If I am not mistaken, the original RCA Ampliphase transmitter had a tube-type exciter and might qualify as an all-tube transmitter. Although I never saw a 50 KW version, I did see the 250 KW all-tube Ampliphase at XERF-1570 in Ciudad Acuna, Coahuula (sadly, it was still in pieces). That assumes, of course, that you consider the Ampliphase to be a Real Transmitter and not merely an exercise in all-night transmitter tuning.

    It should be noted that this article does not describe the KAAY transmitter as it was installed. RCA changed the final and modulator tube type from the 9C22 to a 5671, which had an improved filament and used far less power than the 9C22. Noted Consulting Engineer Jack Sellmeyer explains it all: