Topband: two-wire beverage
k4kv at mds-ham.com
Wed Sep 9 06:48:51 PDT 2009
I am preparing for low-band season, after a poor 6M E season ;-(
I had two beverages fed at a common point with a relay switcher in the
woods, one NE and one
I have converted them to dual-wire ones, and they about 700' long each.
Here is the results from the on-line calculator:
Primary impedance 75 ohms
Zoa = 350 ohms
Zot 750 ohms
Zot turns ratio 2.15
Zoa turns ratio 3.17
So, I tried winding the transformers bifilar and that only yielded antennas
that worked only
in the forward direction, NE and NW.
Changed to actual center-tapped transformers and now it is working better,
but I am not sure it
is still right.
The main forward transformer I have is 3:1 turns ratio, with 3 turns primary
and 9 turns secondary, tapped at 4.5 turns. From my feeble understanding,
this is to transform the 750
ohm feedline impedance to 75 ohm coax. I know, not exact.
The reverse transformer 350ohm antenna to 75 ohm coax: 2 turns primary to 4
The reflection transformer is 750 ohm feedline to 350 ohm antenna. It has 3
center tapped at 1.5 turns and two turns secondary to ground rod.
Do you see a problem with this thinking?
Also, I have a control board in the shack with an AC power input that allows
me to switch
all 4 directions.
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