> -----
>
> On Jun 29, 2008, at 8:19 PM, Gregg Seidl wrote:
>
> > I replaced my trusty A-3S with a Bencher Skyhawk.I wanted to take
> > the A-3
> > and mount it at 40 feet on my new Rohn 45 tower.It is
> mounted about
> > 5 feet
> > above the guys but it is NOT at the top of the tower.The
> tower is 85
> > feet
> > tall.I wanted to point it E/NE and jsut leave it there.
> > We got it up for FD and noticed the SWR was not very
> good.It was
> > great
> > on the top of the old tower.We changed nothing.The guys are
> farther
> > away
> > then they were with tower top monting.The guys are steel
> but are 77
> > feet
> > long.The driven element is about 2 feet away from one of
> the legs of
> > the
> > tower.
> > I'm lost as to why it changed,any ideas.The swr is about
> > 2.5:1.Feedlines
> > check good.Balun is good.
>
Greg,
I had an A3 side-mounted on my 25g 70' tower at 40' for many years. it
worked great and was unaffected by the presence of guy wires....best I could
tell.
Is the SWR a consistent 2.5:1 across the bands?
What tests have you done to verify the condition of your coax feedline?
What test did you perform to verify the condition of the balun?
I'm using a coax choke balun as described in the A3 instruction 'manual'.
Like Bill said, if you have access to a good grid dip meter (forget using an
MFJ259), you might take down the driven element and check the traps. If
they check good, you may have to take down the beam and check the traps of
the director and reflector elements.
I've got a collection of notes I gathered and put together on refurbishing
my A3 a number of years ago. the expected resonant frequencies are listed
as well as how to disasemble the traps.
http://www.hal-pc.org/~kg5u/a3refurb.txt
73 and good luck.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|