----- Original Message -----
From: "Dan Sawyer" <dansawyer@earthlink.net>
To: "amps" <amps@contesting.com>
Sent: Saturday, November 19, 2005 8:58 PM
Subject: [Amps] hit a wall on bi-directional couplers
> All,
>
> I have hit a wall on bidirectional couplers for HF. I have breadboarded
> the bi-directional portion of the following attached bi-directional
> coupler circuit. It appears in principal to be the same as the circuit
> in the arrl antenna handbook.
Hello again Dan,
I have not seen the circuit you refer to in the handbook. My latest
copy is 1977.
>
> http://www.ramseyelectronics.com/downloads/manuals/PM10DC.pdf
>
The circuit shown in fig. 1, page 5 looks like a 180 degree hybrid.
> I did not terminate either coupler output, I simply sampled them for
> voltage with a high impedance scope probe.
Hybrids are difficult to construct. Symmetry is a must.
It is wise to use attenuators on the output ports when making
measurements with them.
The net net is there is no
> difference between the outputs and they are both high, about 3 db down
> from the input.
If you terminate port A and feed port B you have a 2 way power divider
that will give you equal outputs at D and C and they will be 3db down.
Plus insertion loss.
I did not use a 'binocular' transformer but used two
> tube types in the same configuration. I was very careful to wind the
> transformers exactly as described in the text. The feed through is a
> piece of copper wire centered in the transformer by an insulator. The RF
> output is terminated in 50 Ohms.
>
> I would appreciate pointers, advice, links to primers, or links to
> alternatives. Thanks - Dan kb0qil
>
If what you are really looking for is a bi directional coupler for your
vector voltmeter I would suggest a Model CH-130 made by ANZAC.
The coupling is 30db but it will handle 500 watts and covers the entire hf band.
Must be one out there somewhere.
Mike k1ern
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