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      General Electric Co., Syracuse, N. Y.  | 
    
GE BT-25 and 50 Series
General Electric was the manufacturing arm for the companies building early broadcast transmitters. Westinghouse was heavy into the control circuitry and RCA packaged a lot from these two.
The
GE 50 kW Series:| 
       pre-1935  | 
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| GE (with some help from Westinghouse) built many of the early transmitters, especially the higher powered ones. In fact, RCA did not build their own transmitters until the mid-1930s, actually selling GE models with and RCA label. Even the RCA 50A and 50B/C were really GE transmitters with an RCA nameplate on it. It was after the breakup | |
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       4BT-25-A (1947?)  | 
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  GE was first permitted, under the Consent Decree, to market
      its own transmitters in 1935. The first 50 kW unit by GE had the model number
  BT-25-A. Apparently only a few were made:
      
      
  WPTR 1540, WCKY, WPTR, KCBS, and KFRE (later KFIG) The BT-25 was a high-level plate modulated transmitter. BT-25 used Westinghouse WL5891 tubes (one spare in each cubicle, total 6). 
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       4BT-25-A1  | 
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    KCBS, San Francisco Installed 1963  | 
  
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     4BT-50-A  | 
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The 4BT-50-A used Machlett 6427 tubes in a far more compact cabinet design.
 Bill Frahm says:  KOA, KNX, WSM  had versions of it. Seems to me
the  I had the GE BT50-A1 in Boise, built in 1964 -65. Our A1 had the 4400 v inductor on the primaries of the three 480 v pole-pegs. Other stations using the GE transmitters include KRLD, KPOL, WLS and others 
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     4BT-50-A1  | 
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     4BT-50-B  | 
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    KPOL, Los Angeles (BT-50-B???) | 
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     BT-50-C BTC-50-C  | 
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| There may have been a 50C as an upgrade from the 50B, but the BTC-50-C was built in Canada. | |
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    The Canadian General Electric BTC-50-C |