[TowerTalk] steppir v. lpda

[Steve, W3AHL]

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 at rochester.rr.com>
To: "Tower and HF antenna construction topics." <towertalk at 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..