Since the Tennadynes that I've seen have a 50 ohm nominal feed point Z, not
200 ohm, the issue is a little different.
Having a balun at the front of the boom isn't a problem if it's constructed
correctly. Using a coil of coax bundled up and flapping in the breeze will
eventually lead to failure probably. A better solution is to use ferrite
core balun is mounted in a weatherproof plastic box with its output
terminals screwed into the boom / transmission line.
Some Tennadyne owners do place the 1:1 balun at the mast plate and claim
there is no significant difference in the pattern.
What affect the feed line imbalance has in either case hasn't been evident
in the few field measurements I've seen posted. Whether it is enough to
justify constructing a custom balanced feed line back to the mast is
doubtful, if a couple of ferrites at the mast are effective.
LPDA's that do use a 200-ohm transmission line boom usually have a feed
point Z of 95-110 ohms.
Steve, W3AHL
----- Original Message -----
From: "Gene Fuller" <w2lu@rochester.rr.com>
To: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Sent: Saturday, January 23, 2010 4:23 PM
Subject: Re: [TowerTalk] steppir v. lpda
> For the umpteenth time,ehy not make up 200 ohm line,using 1/4" copper
> tubing, on standoffs to keep aay from the boom, placing the balun back at
> the mast, where it is accessible.
..snip..
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