I'd vote for a flat top dipole as high as you can get it, with ladderline
feed (or a variety of loops, as others have suggested). 300 ohm or 450 ohm
line will be an easier match than 600 ohm. You can bring the ladderline to a
balun, then your tuner. You may have to experiment with different lengths
for the ladderline...1/2 wavelength feedline at lowesat freq is ideal (allow
for velocity factor), avoid 1/4 wavelength. Also, once in the shack, try to
keep your coax lengths as short as possible as well.
A grounded tuner is less than optimal for keeping open wire line balanced (a
balanced or link coupled tuner is better for this, but you might get by).
Stray pickup by the ladderline should only be a problem if it is seriously
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 proximity to
trees and other objects. Try to have the feedline drop vertically from the
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
----- Original Message -----
From: "Merlin-7 KI4ILB" <merlin-7@sc.rr.com>
To: "Merlin-7 KI4ILB" <merlin-7@sc.rr.com>; <TOWERTALK@contesting.com>
Sent: Friday, February 10, 2006 4:25 PM
Subject: Re: [TowerTalk] ladder line vrs coax
> Opss I made a typo, the top of my parallel dipole is 38 feet up.
> It has 3 elements a 16' a 33' and 66' (each side) (befor they were
> tuned)all conected to the same feed point with an air wound choke at the
> feed point also.
> I also use a mfj deluxe versa tuner II .
> I also have a vectronics antenna analyzer. I have ordered a coax switch
so
> that I can switch between the hf rig to the antenna or the antenna and the
> analyzer. (I am getting tired of whistling lol )
>
> So I guess my question here is, if I put up a 135' or so, flat top fed
with
> ladder line would there be much difference between the two? pros and cons?
>
> As for birdies. I never thought of that one. There are 5 computers here
and
> at least 2 are on at any one time.
>
> Thanks
>
>
>
> > I am a bit confused here.
> > I have an inverted parallel dipole setup now fed by coax with an air
> wound coke at the feed point.
> > the feed point is about 28' high and the ends are about 18' high.
> > I picked up a flat top kit fed with ladder line.
> >
> > What are the pros and cons between the two other than less loss on the
> flat top?
> >
> > Thanks
> > Joe
> > KI4ILB
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|