[Amps] Sampling RF at input and output of an amplifier

[peter chadwick]

One of the WW2 IFF test sets for VHF IFF had a PL259/SO239 TEE that did precisely that. An M35X  (X = something or other)

73

Peter G3RZP


========================================
 Message Received: Jan 16 2014, 07:00 PM
 From: "Karin Anne Johnson" <karinann at tampabay.rr.com>
 To: amps at contesting.com
 Cc: 
 Subject: [Amps] Sampling RF at input and output of an amplifier
 
 Here's a really simple sampler/signal pick off device.
 1 - Use a UHF TEE connector. Shown below.
  
                     =================
                     |               |
             Female  >---------------<  Female
                     |       |       |
                     ======  |  ======
                          |  |  |
                          |  |  |
                          |  \/ |
                            Male
 2 - Remove the center male pin by unscrewing it from the connector.
     Not all center pins will be able to be removed by simply unscrewing
     the center pin.  Find one that will. The remaining female to female
     center pin will be floating free in the connector dielectric.
 3 - Use a UHF Female to Female barrel connector, and screw it into 
     the Male port you just removed the center pin from.
 4 - Connect your amplifier or rig output to one of the Female ports and
     the other Female port to a dummy load.
 5 - Connect the "Tap Point"(the Male port on the Tee which now has a 
     Female barrel screwed into it) to your measuring device(ie: scope).
 6 - As measured on an HP8753C VNA, the tap port is better than 90 dB down
     from the main line at 28 MHz with a 50 dummy load connected to the 
     thru line.
 7 - The stray coupling capacitance between the main line and the center pin
     on the inserted female to female barrel provides a capacitive pick off
     point for connection to a measuring instrument.  The signal is not 
     calibrated relative tot he main line but can be used for monitoring
     at reduced mainline amplitudes.  
 
         Karin K3UU
 
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