Winding Beverage RX Balun de K0FF
Today a friend decided to run a receive Beverage on 160 and asked me to make
a transformer for him. The results are in these pictures:
http://homepages.dstream.net/K0FF/160/BevBox/Inside.jpeg
and
http://homepages.dstream.net/K0FF/160/BevBox/Outside.jpeg
This one is a 9 to 1, BALanced (coax) to UNbalanced (Beverage wire)..hence
the word BALUN.
It is set up for 50 Ohm cable ...I myself use 75 Ohm double shielded for the
same purpose, but Bill wanted 50 Ohms so here it is. No particular
difference especially, except that the 75 Ohm stuff can be had
inexpensively and in 100%
shielding, and I figure if you go to the trouble to run a real decent
Beverage, why invite other uncontrolled sources of noise.
Anyway this one is four windings of 16 turns each to make both the primary
(3 windings)
and secondary (1 winding....the impeadance ratio is the SQUARE of the
windings ratio),
and the little paper tags you see are to help me remember
which phase is which. The core is an FT50-75 and I've had good
results here with similar layouts.
There are two schools of thought on the windings that go to the coax cable.
On has the transformer in a plastic box, or otherwise isolates the coax
shield from ground at the antenna end. The low side of the antenna winding
is the only thing going to ground, and the two wires on the coax side go to
the connector. I myself don't like this way, and invite discussion as to why
it may be preferred. The arrangement shown here uses a metal box, and the
shield
is automatically grounded too. Actually I've tried it both ways but fail to
be able to
discern a difference, and given a choice, I always ground everything that
can be.
Now it took me more time to get the label to print out the way I wanted than
it did to make the device. Finally got the wording the way it should be, and
then affixed it to the panel with an overlayer of C-Line do-it-yourself
laminating plastic, for weather proofing. Anyone got a lead on a nifty
(free) program for printing
control panels, graphics for equipment, or especially dials and meter faces?
Happy Building, Geo>K0FF
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