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[AMPS] RF power calibration

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Subject: [AMPS] RF power calibration
From: (John T. M. Lyles)
Date: Thu, 27 Jul 2000 09:46:27 -0600
Having worked for Delta Electronics, Inc. in Virginia, a long time 
ago, I remember that we had an in-house RF calibration system 
approved by the FCC. We built RF ammeters for MW broadcasting, and 
the TCA series is probably the industry standard now, since Weston RF 
ammeters are ancient. The TCA used a current transformer and a 
specially linearized RF diode rectifier circuit. However, to 
calibrate these was the question. We had a homemade thermal transfer 
standard. The RMS power of a clean sinewave at 1 MHz would heat one 
side of a Ballentine dual thermocouple the same as DC. We would dial 
up the DC current from a Fluke current standard, which went out to 
NIST regularly for recalibration. This would then be balanced against 
an RF level control from a generator, to get a null reading of the 
output. (I assume that they still make these). I'm missing a few 
details now, its from memory over 20 years ago that I worked there.

Then we had the RF level traceable to NIST. The TCA was fed the same 
RF (coming from a small lab power amplifier made by ENI). We set them 
to within 1% I believe (no modulation). The point is that it is 
possible to get FCC approved RF power measurements with things 
besides an Agilent Signal Generator or Bird Wattmeter. I also 
remember that Eaton/AIL used to make a huge broadband RF wattmeter 
calibration system that had some sort of transfer standard.

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