Radio WC6W wrote:
>
> That circuit is at least 40 years old... Why it has never been put
>in the "handbook" and properly described is just one of those mysteries
>of the universe...
>
Bruene, who invented the circuit, described it in QST in April 1959 but
for some reason the description has never found a permanent place in
the handbooks. About a year ago I summarized Bruene's original article
for my magazine column, and there's a PDF at:
www.ifwtech.co.uk/g3sek/inprac/best-of.htm#bruene
As Roger said, the toroid acts as a current transformer to sample the
current, and the caps act as a voltage divider to sample the voltage. To
set the bridge up correctly, those two samples must be equalized so that
the 'reflected' reading is zero on a matched load. The trimmer cap
adjusts the voltage divider to do that.
So there's your adjustment procedure - connect a good 50 ohm load, and
adjust the cap for a null in the 'reflected' reading.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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