2m vertical dipole for FM
 

Does anyone have a plan that I can build without a gamma match. Just
something that is a straight forward dipole. Thanks all.

On Sun, 12 Oct 2003 04:17:59 GMT, "Fart Blossom"
wrote:

Does anyone have a plan that I can build without a gamma match. Just
something that is a straight forward dipole. Thanks all.


Use your imagination.
I used two pieces of 1/2 inch copper pipe, a plastic "T" and a 3'
length of thin wall conduit.

To be neat you can put pipe caps over the ends of the 1/2 inch pipe.

Cut them to length, pull the coax through the thin wall, out through
the "T" with the braid to one side and the center conductor to the
other (solder each and keep the leads as short as possible.. Use hose
clamps, tape, tywraps, or what ever to fasten the thin wall to a
support. Make sure the copper pipes are in the vertical plane.

You can also build 4 folded dipoles, out of copper pipe and fittings.
Feed it with a 90 ohm coax cable harness, get some gain and that
antenna is rugged.


Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)

"Fart Blossom" wrote in message ...
Does anyone have a plan that I can build without a gamma match. Just
something that is a straight forward dipole. Thanks all.

Shouldn't need one if center fed. But you will need matching for any
base fed 1/2 wave. I usually use the "gamma loop" setup. Same as most
of the cushcraft verticals. Myself, for a simple 2m antenna, I prefer
a simple 1/4 wave ground plane with sloping radials. No matching
needed, and a fairly good pattern on the horizon. Just as good as a
1/2 wave usually. In theory, there is only about .3 db difference
between the two. In actual practice on VHF, many times the ground
planes work better due to better decoupling of the feedline compared
to a 1/2 wave with no extra decoupling. MK

Fart Blossom wrote:
Does anyone have a plan that I can build without a gamma match. Just
something that is a straight forward dipole. Thanks all.


Ok, this works ...

Work with 146 MHz, middle of 2m. 468 / 146 ~ 3.2 ft for 1/2 wavelength,
total length of dipole. Each half of that (1/4 wl) is ~ 19.23 inches.

Asuming you have some coax of the right type/length etc. with whatever
connector you need for your radio, gently cut the outer insulation about
19.3 inches from the free end. Pull the whole piece of outer
insulation off the braid.

Fold the braid back over itself toward the radio end for the complete
length of the stripped braid, 19.3 inches.

Now from the end you have a 19.3 inch section of only the center
dielectric and inner conductor, followed by a 19.3 inch section where
the braid has been folded back over the outside of the coax, and then
the rest of the coax looks normal.

You need to seal up the approx 40 inches on the end of the coax that
you've been working with. If it's mounted outside I would also rig it
inside a capped piece of pvc pipe.

There, clear as mud ...