On 9/24/2012 7:20 AM, Tom wrote:
I want to build a home made omni for use on tower.

I want to feed it with coax and have lot of wire, copper pipe, tubing,
basic parts.

I have a pretty good tuner and will use the tuner to tune. Can anyone
make a recommendation as to how to make a not so complicated omni
directional antenna that practical?

I am thinking something about 6 to 10 foot in height only, I can make
gnd planes, but something I can tune to get most bands and simply omni
function. I want to get all bands and I run barefoot and just want to
get on the air with simplest, least complicated, easiest to build omni.
I don't need a electronics lesson in engineering design, just a website
or two explaining the simple build of the magical omni fed with coax
that is the best I can get for my situation.

Thanks

73s


Use the tower!

KD7HB

I thought of that but there are a bunch of other things on there like TV
antennas, dishes, clothes lines, back yard lights, etc etc. Stunt it, just
wanted to throw up a crazy idea, I know it is a very broad question. What is
the smallest thing I could use with a pretty good tuner? On top the utility
tower?



"Paul Drahn" wrote in message
...
On 9/24/2012 7:20 AM, Tom wrote:
I want to build a home made omni for use on tower.

I want to feed it with coax and have lot of wire, copper pipe, tubing,
basic parts.

I have a pretty good tuner and will use the tuner to tune. Can anyone
make a recommendation as to how to make a not so complicated omni
directional antenna that practical?

I am thinking something about 6 to 10 foot in height only, I can make
gnd planes, but something I can tune to get most bands and simply omni
function. I want to get all bands and I run barefoot and just want to
get on the air with simplest, least complicated, easiest to build omni.
I don't need a electronics lesson in engineering design, just a website
or two explaining the simple build of the magical omni fed with coax
that is the best I can get for my situation.

Thanks

73s


Use the tower!

KD7HB

I thought of that but there are a bunch of other things on there like TV
antennas, dishes, clothes lines, back yard lights, etc etc. Stunt it, just
wanted to throw up a crazy idea, I know it is a very broad question. What is
the smallest thing I could use with a pretty good tuner? On top the utility
tower?

How about a car/truck "screwdriver" antenna?

I have a pretty good tuner and will use the tuner to tune.

The combination of a short vertical, a tuner in the shack, and a coax
feed, is not a particularly happy one.

You *may* be able to tune it, in the sense of presenting a load to
your transceiver which won't cause its output section to complain or
leak blue smoke. However, the losses in the tuner, and (particularly)
in the coax feedline, are likely to be very high... you won't get
much signal out, and you may end up with high enough voltages on some
sections of your coaxial feedline to cause arcing (even at "barefoot"
power levels!)

So, the two approaches I can think of which might work would be:

(1) A "screwdriver" antenna or equivalent... a vertical whip (longer
is better) and a remotely-adjustable loading coil.

(2) A vertical whip, and a remote-controlled (or self-controlled)
antenna tuner / transmatch mounted right at the base of the whip.

In either case, you'll probably need to use the tower itself as the
"ground" (counterpoise) for the tuned antenna... plan on running some
heavy, low-impedance braid from the tuner to the antenna mount point.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Tom" wrote in message ...

# I thought of that but there are a bunch of other things on there like TV
# antennas, dishes, clothes lines, back yard lights, etc etc. Stunt it, just
# wanted to throw up a crazy idea, I know it is a very broad question. What
is
# the smallest thing I could use with a pretty good tuner? On top the
utility
# tower?

With an antenna that short, you will need a ground for it to work against.
If you can manage that with guy wires etc., let me relate my recent
experience.

I use a vertical mounted above a metal patio cover, which is about 15x30
feet, roughly 10 feet off the ground. The feedline is 15 feet of RG8 to a
tuner.

Initially, I installed a 9 foot CB whip antenna. It worked quite well on 12
and 10 meters. 17 and 15 meters were hard to match, and marginal contacts
were made on 20 meters.

I replaced that whip with a 14 foot whip. It worked quite well on 20 meters
through 10 meters. I was quite happy with it, but got the bug to experiment
some more.

lastly, I replaced the whip with a 17 foot whip. It works well on 30 meters
through 15 meters, and can be brute force loaded on 40 meters through 10
meters. I don't have much performance info, since the bands have been
stinko for a while.

Both the 9 foot whip and the 14 foot whip did a credible job during the last
set of DX contests, with the 14 foot clearly being better.

In summary, if the antenna is 8-10 feet, I wouldn't count on getting much
performance other than on the higher bands, say 15-10.