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Re: [Amps] Power metering in linears

To: robrk@echomatrix.net, "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Power metering in linears
From: craxd <craxd1@ezwv.com>
Date: Thu, 07 Oct 2004 14:13:42 -0400
List-post: <mailto:amps@contesting.com>
Rob,

You are correct on this. Most use a 1N270 or so, but I'm not sure what would be needed for that wide of a range.

Will Matney


robrk@echomatrix.net wrote:


Don't think any diodes in the circuit are linear from 160 to 10.



Tom,

Stripline type RF sensors are narrow-banded and generally won't work
with that type of band spread. The toroidal transformer should work if
the core is rated for the complete frequency range like 3-30 MHz. If
not, you may have to add a switch to kick in another potentiometer just
for 80 meters and maybe 160 meters. To get the meter to null is another
thing and has to be done to read forward and reflected power. You may
just try different toroids first before doing any modifications.

Will Matney


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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