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[Amps] Power metering in linears

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Subject: [Amps] Power metering in linears
From: "Thomas Hoeppe" <thomas.hoeppe@asamnet.de>
Date: Wed, 6 Oct 2004 20:38:59 +0200
List-post: <mailto:amps@contesting.com>
Hello technicians,

I was adding a power meter to a new homemade linear. I used the directional 
coupler of the "Digital PEP Wattmeter and SWR calculator" from an old ARRL 
handbook (1987). I did not get a too deep null on calibrating, so the 
directivity was only 20 dB. As I only wanted to monitor the output of a linear 
with that coupler, the directivity was sufficient. 

The problem: The output voltage for a given power is the same from 40-10m, but 
nearly null on 80m and different on 160m.

Then I tried the design from the linears in the W6SAI handbook. They use Amidon 
50-6 toroids. The output voltage ón 160 is about 1/2 of the voltage on 10m. 

Has anyone successfully built a directional coupler with constant frequency 
behaviour from 160-10m?

I would like to have proven designs.

Thanks!

Tom, DJ5RE
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