On Sun, 4 Jan 2004 08:51:34 -0700, "Ken Bessler"
wrote:

Thanks for the info, Richard - I went to Eham.net and read the
reviews on the all bander. Not all were good so I started looking
at the other reviews for ideas. Found the MFJ-1788 G5RV
antenna. I'm usually a bit suspicious about MFJ products but
this one got good reviews.

So, what do you think about the G5RV for my situation? The
apex would be at 35' and the ends would be about 20' The 34'
of ladder line would reach my window feedpoint just fine then
I could make a coax choke (MFJ says 10 turns @ 4-6" dia) and
then feed it to my LDG tuner. the coax run would be about 8'.

A note on choke construction - I use plastic forms to wind the
coax then glue the turns together with superglue and baking
soda. I only have two smooth plastic forms avaiable - a 2-5/8"
and a 5 inch. So, I could make a 10 turn, 5" dia choke for this
new antenna.

Your thoughts?

Ken KG0WX


Hi Ken,

Your recipe for a choke sounds quite suitable. Keep in mind all such
designs are optimized somewhere and marginal elsewhere. What you've
described will undoubtedly do the job, peaking in the 20-30M bands and
tapering to each side. The fact of the matter is that few measure
where their chokes resonate (thus providing the greatest isolation) or
how much Q they exhibit. Usually, the proof of isolation is found in
performance. That is, did it clear up transmissions getting into the
home electronics? If it did, no one will care the line still radiates
- unless such lax isolation fills in nulls you need in a pattern to
kill neighboring noise or strong stations.

As for the G5RV. It was designed to a length to be suitably tuned in
a majority of bands back in the stone age. Band plans have changed
somewhat (WARC and all) to confound that claim. That aside, the
combination of coax and ladder line was something of a marketing idea,
you are just as well off by simply using ladder line all the way back
to the tuner (or the BalUn heading into the tuner, make sure it is a
Current BalUn design, as the ones inside tuners are mickey mouse
Voltage designs). So, having stripped away the trademark coax/ladder
combo, you can progress to the next step and simply erect the highest
longest dipole and be done with it. You are going to be doing a
tune-up anyway, so having excess length draped through trees and
limping ground ward has no inherent merit. It won't hurt that much
either, but no magical properties will be observed through what we
call "appelation gain" (that extra 3dB because the vendor put a name
to it like G5RV).

A buddy of mine had the classic G5RV and it served suitably well
(coming no where close to his beam where the bands overlapped) until
one dark and stormy night when he encountered a higher than normal SWR
against a lot of power. The BalUn rattled like a mariachi after that
and the antenna was quite deaf.

73's
Richard Clark, KB7QHC