KL7UW


1296 30W DRIVER-AMPLIFIER

  

  Jan, 2015 

  I have begun construction of the 30w 1296 Driver Amplifier from the kit sold by N9RIN.  
  It consists of a single Infineon PTF 1002 LDMOS FET with 30w output at 28v, 2A.  
  Quiescent load is 360ma and gain is 13dB so it drives with 1.5w.  I will run it between
  18-20w at 24v to provide drive to two 150w W6PQL amplifiers for combined output of 300w.

  The 2.5 by 3.75 inch pc board is shown, below.  It will be mounted on a 5.375 by 5.00 by 
  1.375 inch aluminum heat sink with 1 inch high fins spaced five per inch.  Additional cooling 
  provided with a 4-inch fan.  The board will be enclosed in a 5 by 4 by 3 -inch enclosure
  which will have a opening cut to permit the LDMOS transistor to be directly mounted to the 
  heat sink.  A 3-dB 100w chip attenuator will also be attached to the heat sink at the RF input 
  to the amplifier.  This will allow the transverter to drive at roughly 8w thru the 5.9-dB line 
  loss to the location on the dish to provide 1w drive.

  The driver will be usable at half power to drive one of the 150w RF amplifier decks while 
  the second 150w amplifier is under construction.

  Test Results Jan. 23 

  DC tests were first made with 12v supply; then 28v was used for final tests, below
  Vgq = 4.22v with Idq= 327 ma (no RF drive)  Supply voltage is dropped thru two 5w 3.3-ohm resistors in parallel
  to keep Vds near 24v under full load.

  Drive  Input  Output*  Vds  Id  
  1.0w   0.5w   4.5w   25.82v   1.3a
  1.5w   0.75w  6.0w   24.92v  1.87a 
  2.0w   1.0w   13.0w  24.80v  1.94a
  2.5w   1.25w  20.0w  ---        ---
  3.0w   1.5w   22.0w  24.10v   2.36a 

  *After running the tests using a 50E element and Bird-43 power meter comparisons were made at 10w with a 
  10K element and the 50E element read 1.3 times higher.  Neither element is calibrated so I cannot use either 
  as an absolute power reference. The PTF 1002 was only mildly warm after all tests so heat sink is working fine.

  Photos of N9RIN 1296 PA:








































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