[TowerTalk] ladder line vrs coax
k0dan at comcast.net
Sat Feb 11 11:22:53 EST 2006
Try it with what you've got, you have nothing to lose and it could work
fine. Since it sounds like you don't have a link coupled (ala EFJ Matchbox)
or balanced-balanced tuner, then you'll probably need to use a balun at the
tuner. Some will say a 1:1, most tuners use a 4:1, and you might need a
higher ratio depending on the impedances of the antenna + line (and you
can't predict these very well until you try them in your real world).
You'll know you'll need the balun if you get RF feedback in your rigs, RF
burns on your lips, can't get a good latch from the tuner, etc.! Try the
setup with low power first, and if you have success, gradually increase
power and see if things change.
If you have troubles with pickup & radiation from the feedline, you may have
to take further steps to better balance it.
Suggest you read some of these articles on these links, they describe your
situation better than I can:
----- Original Message -----
From: "Merlin-7 KI4ILB" <merlin-7 at sc.rr.com>
To: "k0dan" <k0dan at comcast.net>; <TOWERTALK at contesting.com>
Sent: Friday, February 10, 2006 9:04 PM
Subject: Re: [TowerTalk] ladder line vrs coax
> I was not planing on using any coax at all. My antenna tuner has
> for bal. line.
> Is there a problem using this connection without a balun?
> Also the tuner is grounded.
> > I'd vote for a flat top dipole as high as you can get it, with
> > feed (or a variety of loops, as others have suggested). 300 ohm or 450
> > line will be an easier match than 600 ohm. You can bring the ladderline
> > balun, then your tuner. You may have to experiment with different
> > for the ladderline...1/2 wavelength feedline at lowesat freq is ideal
> > for velocity factor), avoid 1/4 wavelength. Also, once in the shack,
> > keep your coax lengths as short as possible as well.
> > A grounded tuner is less than optimal for keeping open wire line
> > balanced or link coupled tuner is better for this, but you might get
> > Stray pickup by the ladderline should only be a problem if it is
> > out of balance. If the currents are equal & opposite in both legs, the
> > feedline line should neither radiate nor pick up signals. Make sure both
> > dipole elements are the same size and heigh above ground. Avoid
> > trees and other objects. Try to have the feedline drop vertically from
> > center of the antenna, don't let it run parallel to or get close to the
> > dipole elements. There is plenty on this topic online and in the various
> > handbooks.
> > Goodluck & 73
> > Dan
> > K0DAN
> TowerTalk mailing list
> TowerTalk at contesting.com
More information about the TowerTalk