I've always used a feedline "loop" that hangs out and down from the tower
leg that's half-way on the rotation circle, is attached to the boom a few
feet out from the mast, and is long enough that it doesn't impede antenna
rotation in either direction. I recently saw an installation with the
antenna mounted about 2 feet up the mast from the tower top, with the
feedline coiled about 2 turns loosely around the mast rather than hanging
down. The antenna end of the coax was attached at the bottom of the
mast-to-boom plate. The arrangement looked like those coils of cable that
the TV trucks deploy when they raise their microwave towers, but only a
couple of turns to the coil. When rotated in one direction the coil got
tighter to the mast, but not touching it. In the other direction the coil
got looser.
My question is.... is this a good idea? I have never seen it before, so
maybe it isn't in widespread use, which makes me wonder why not.... as it
"appears" that it would put less stress on the coax than the usual U-shaped
arrangement.
Any comments or experiences about this?
73, Jerry K3BZ
----- Original Message -----
From: "John Elsik" <wa5zup@msn.com>
To: <towertalk@contesting.com>
Sent: Monday, July 23, 2007 11:58 AM
Subject: Re: [TowerTalk] Antenna/mast height above tower?
> Since most tower manufacturers spec so many sq ft, 1' above the top of the
> tower. Then mounting the antenna 1' above the top would seem reasonable.
> The main thing is to have enough room for the cable loop, so it does not
> snag on anything.
>
> John
> wa5zup
>
>
>
>> From: km1h@jeremy.mv.com> To: rusty_atkins@yahoo.com;
>> towertalk@contesting.com> Date: Mon, 23 Jul 2007 11:08:41 -0400> Subject:
>> Re: [TowerTalk] Antenna/mast height above tower?> > 1 inch. As long as no
>> part of the antenna or mount scrapes the tower you are > OK.> > Carl>
>> KM1H> > > ----- Original Message ----- > From: "R Atkins"
>> <rusty_atkins@yahoo.com>> To: <towertalk@contesting.com>> Sent: Monday,
>> July 23, 2007 10:08 AM> Subject: [TowerTalk] Antenna/mast height above
>> tower?> > > >I haven't seen many recommendations on this. I've googled
>> and searched > >eham.net to no avail.> >> > What is the minimum height
>> above the tower top shelf recommended for an HF > > beam (KT34A, FWIW).
>> I'm trying to run as short of a mast as possible > > without impacting
>> performance of the antenna.> >> > Thanks!> > Rusty> > K0FE> >> >> >> >> >
>> > >
>> ____________________________________________________________________________________>
>>
>> > Luggage? GPS? Comic books?> > Check out fitting gifts for grads
> at Yahoo! Search> >
> http://search.yahoo.com/search?fr=oni_on_mail&p=graduation+gifts&cs=bz> >
> _______________________________________________> >> >> >> >
> _______________________________________________> > 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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|