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Author Topic: Using Bird Attenuator for Dummy load ??  (Read 1506 times)
N2OAM
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Posts: 26




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« on: September 11, 2011, 06:09:45 PM »

             I have a large (2KW) Bird 30db attenuator. I believe 30db is a factor of 1,000, so 2KW in gives me 2 watts out.........Now, if I run the output of the attenuator into a 50 watt (LOTS of head room) dummy load, I can use this setup as a 2KW dummy load ?? Almost sounds too good to be true!
   
             I will be using this with an Alpha 86 and a Ten Tec Titan 425. I would like to be sure this setup will work the way I think it will......... I don't want smoke a pair of 3CX800A7's.

             Thank you for your input.

73 de bob,
n2oam
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W8JI
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« Reply #1 on: September 11, 2011, 06:22:46 PM »

             I have a large (2KW) Bird 30db attenuator. I believe 30db is a factor of 1,000, so 2KW in gives me 2 watts out.........Now, if I run the output of the attenuator into a 50 watt (LOTS of head room) dummy load, I can use this setup as a 2KW dummy load ?? Almost sounds too good to be true!
   
             I will be using this with an Alpha 86 and a Ten Tec Titan 425. I would like to be sure this setup will work the way I think it will......... I don't want smoke a pair of 3CX800A7's.

             Thank you for your input.

73 de bob,
n2oam

My standard bench loads are a 2kW Bird 30 dB attenuator (no termination is required) and when I need high power a water cooled 50 kW 30 dB attenuator with a 3" flange.

Neither requires any pad, because a 30 dB attenuator has 60 dB return loss. Any load you add is meaningless.
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K2DC
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« Reply #2 on: September 14, 2011, 08:33:24 AM »

Bob,

   Tom's right, a load on the attenuator output is not at all necessary.  I've used open-ended attenuators many times as a calibrated mismatch for testing.  For example an open-ended 3 dB pad presents a VSWR of 3:1, and a 10 dB pad is 1.22:1.  Your 30dB attenuator with nothing on the output is a 1.002:1 VSWR, which is probably as good or better than most Bird high power loads.

73,

Don, K2DC
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