This is the Hot Glass Archive Section of
The Broadcast Archive

Maintained by:
Barry Mishkind - The Eclectic Engineer
Last Update 11/22/08

To a veteran broadcast engineer, there is nothing quite like the glow of the glass tubes in a transmitter. The Modulator and Power Amplifier tubes are among many things missing in solid-state transmitters, however, even they had morphed into ceramic tubes at higher powers.

Still, the pulsing glow of the Modulators and the warm bright PA's of a well operating transmitter ... well, it really doesn't get any better.

Here is a sampling of the Hot Glass from the Tube Era of broadcasting:

 

1 kW and Under

  Tube Some of the transmitters that used these tubes.
  3-500Z Collins 828D-1, Continental 314R-1
     
  4-250A Collins 550A-1

4-400A Collins 20V series
  4-500A McMartin BK-1000
  4CX3000A Gates Vanguard
  5-500A Collins 820D-1 and 820D-2

450TH  
     

833A Gates BC-1T, BC-1G
     

 

5 kW 

  Tube Some of the transmitters that used these tubes.
     
  3CX2500  
  3CX3000  
  3CX5000  
  4-1000A McMartin BK-2500, BK-5000
  4CX5000A  
  4CX10000A  
     
  5762  
  891R  

892R Most non-Western Electric transmitters. This RCA tube had very brittle filaments, according to Bob Groome
  DX-516  Longer life than the 892s?

 

10 kW 

  Tube Some of the transmitters that used these tubes.
     
  3CX10000  
  4CX5000A  
  4CX15000  
  5762  
  891R  

892R Most non-Western Electric transmitters. This RCA tube had very brittle filaments, according to Bob Groome.
     
     
     
     

 

50 kW

  Tube Some of the transmitters that used these tubes.
     
  4CX3500A  
     
  5671 1947 - RCA made this to replace the 9C22. 
  6696  
  6697  
  893R RCA Tube

893AR KEX, Portland used this one
  898 RCA 50C 50D  (this is essentially an 862 with filaments modified for three phase heating).
     
  9C22 Used in the original BTA-50F, replaced in 
     

WL5891 Westinghouse 50HG-1, GE BT-25, Gates BC-50B and BC-50C
  UV207 GE  (WGY)

Stan Adams says: "Parasitics would often cause overheating and would blow the grid low value resistors and the plate caps. It did not like operating at certain voltages."

  UV 862 RCA  50B, 50C  (RCA's version of the GL-862A)
water cooled
  UV 863  
  GL-862A early GE transmitters
water cooled.

 

Really "Big Glass"

  Tube Some of the transmitters that used these tubes.

320A Used by J.O. Weldon for some of the borderblasters
  GL-862A WLW's 500 kW