On Feb 23, 7:35 am, Cecil Moore wrote:
wrote:
What he wants to build is what outbacker sells.

Why would he want to build an antenna that,
on 75m, is only 12% as efficient as a good
bugcatcher?
--
73, Cecil http://www.w5dxp.com

I dunno. Probably weight, and being able to avoid the
usual industrial strength mount required for the heavy
antennas.
But using a helical stick is no sure route to disaster.
I've used a few that were so close to bugcatchers in
performance you could hardly tell the difference on the
air.
But... they were modified sticks, and not the usual you
buy at a store.
IE: if I want a 40m stick, I don't use a regular 40m version.
I use a 20m version and a longer stinger. I also try
to use one that has the bulk of the windings near the
top to improve current distribution. The helical whips
act the same as a lumped coil antenna in this regard.
You will have a more linear current distribution if you
wind most of the coil near the top, and then use a pretty
long stinger above it.
Being that in most cases ground losses are higher than
coil losses, often the ground loss swamps the coil
loss, and you end up not seeing as large a difference
as you would expect.
I often see the same comparing larger lumped coils.
IE: a 3 inch vs a 6 inch diameter coil..
In theory the 6 inch should be quite a bit better, being
less turns are needed, but often in the real world the
difference is hardly noticeable being the ground loss
is pretty high.
The worst helical whips are the ones that use no or a
very short stinger whip. If you want to use a thin helical
whip, you *must* use a pretty long stinger above the
glass whip if you want any kind of decent performance.
The 20m stick I used on 40m was very stout. But it
was 6 ft of 20m glass whip with the windings at the top,
and 5 ft of stinger. 11 ft total.
Made the car look like one of those RC cars... :/
But that antenna eventually became my present
lumped coil "plastic bugcatcher.
MK