Then explain why a 4:1 balun is needed. Heck I might learn something.
73
Bob K4tAX
----- Original Message -----
From: "Mike Bryce" <prosolar@sssnet.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, July 11, 2013 8:50 PM
Subject: Re: [TenTec] OCF antennas evolution
I quite aware that open line is generally considered lost less feed line.
What threw me was the use of a 1:1 balun instead of a 4:1.
That's the head scratcher.
Mike wb8vge
Sent from my iPhone
On Jul 11, 2013, at 9:32 PM, k6jek <k6jek@comcast.net> wrote:
Mike,
You're matching the antenna system, the antenna and the feed line. You
just can't separate the two. When the antenna impedance at a particular
frequency is different from the feed line characteristic impedance, the
impedance on the line is different every place on the line. You're
matching whatever it happens to be at the shack end of the feed line.
Losses are the reason to put the balun near the station instead of near
the antenna. Open wire line has much lower losses than coax under
conditions of very high SWR. That's the reason we put up with the stuff
which is a royal pain in the arse, just so we can have a ridiculous SWR
and not care about it. And very high SWR is exactly what we have at
almost all frequencies when using a doublet as a multi-band antenna. The
only reason we can get away with such a thing is the low loss of open
wire line. So you want to run that stuff as far as you can before
switching to coax. As long as you can is ideally right into a balanced
tuner, no balun at all.
Jon
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