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Old October 29th 08, 06:42 AM posted to rec.radio.amateur.antenna
Owen Duffy Owen Duffy is offline
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First recorded activity by RadioBanter: Dec 2006
Posts: 1,169
Default Carolina Windom without a balun: go figure

jawod wrote in
:

Well, as an update to my Carolina Windom project, I find that the CW
OCF dipole cut to typical dimensions works well WITHOUT a balun but
does not work at all WITH a balun.

Specifically, a DX Engineering BAL200-H10-AT 4:1 balun. I bought it
to go with a folded dipole from DX Engineering. It worked fine with
the folded dipole and a length 300 Ohm ladder line as feed.

When I use the above balun with the CW cut to typical dimensions and
using a 300 ohm ladderline feed, even RECEIVE is muted...no change
from coax only.

I am fairly sure that the balun is a voltage type and not a choke
type. I also installed a series of ferrite beads from Palomar to choke
the coax near the bottom of the ladderline.

I guess I'm not all that surprised that the CW works without a
balun...the ATU tunes it and sig reports aren't bad. I guess I have
some radiation from coax and a mismatch from coax to ladderline but I
think I can live with that. It's getting cold and I needed to finish
this thing before winter really sets in.

I am clueless as to why the CW failed to work AT ALL when USING a
balun. The internals of the balun look fine.

Any thoughts?


1. Doesn't the manufacturer of Carolina Windom's claim one of the
benefits is feed line radiation? (If you can't suppress it, call it out
as a competetive advantage?)

2. DX Engineering are a bit light on info on the balun, like most
manufacturers I guess... but the title bar of the web page says it is a
current balun. Pity the technical details tab doesn't make it clear.

3. If the design is intended to excite feed line common mode current,
then the device at the top of the feed line is probably a 4:1 Ruthroff
balun which has very low common mode impedance (differently to an
effective current balun).

4. What has 300 ohm line got to do with the Carolina Windom?

Owen