GAMMA MOUNT
BRACKET ASSEMBLY
Now you will need to
get some more sheet metal to build the SHORTENING strap of the gamma
this may vary in size depending on the tubing size and the space
from driven to the gamma match. The gamma match is mounted along the
side of the driven after you have soldered the innner conductor of
the gamma to the center od the SO-239.
See
drawing below for typical gamma match placement and
construction.
Typical Gamma Match
Construction
The spacing of the gamma match is usally about
1.5 to 2 inches from the driven element (Does not make much
difference). To make the SHORTENING strap make a 1 inch strip
about 6 inches long.
Take this strip and bend it around the
driven and over to the gamma. Make sure it folds back over so that
you can drill 1 hole at each end. You can use your own
construction methods and fabrication.
A GAMMA
MATCH
The gamma match is
made from 3/8 inch tubing.
The inner portion is cut from RG-8
coax after you remove the black 'skin' and the copper braid. You can attach 50 ohm coax to this antenna after you
add a gamma match.
Once you have this
antenna put all together you can adjust the match by sliding the
shortening strap and the gamma tube in and out (or up and down
however you look at it) for lowest S.W.R.
------------------------------------------------------------------
A 6 METER
HALO
The 6 meter Halo is
a good antenna that can be used for the car as well as the
house.
This antenna maintains good omni-directional horizontal
polarization.
Basically the antenna is a half wave dipole
bent into a circle, BUT shorter than a dipole for this frequency.
The circumference is 60-70 inches. By using the gamma match (see
above) you can use regular coax. This is a high-Q
antenna, so bandwidth is about 200khz. (Perfect for 50.100Mhz -
50.200Mhz where most of the 6m ssb activity is)
The 2 large discs can be about
4-5 inches round and the small disc about 1.5 inches. Mount the 2
larger discs at the ends of the halo by screwing end caps to the
center of them and then the end caps will go over the ends of the
halo.
Next drill a small hole in one of the larger discs and
the same size hole in the exact center of the small disc. Put a 2
inch bolt through the center and run a nut up the bolt to lock it in
place. Then a nut on each side of the large disc to secure the bolt
to the larger disc.
Mount the gamma rod the same as you did
on the beam (see above), BUT bend the
gamma to match the curve in the halo. Finally take three 2-3
inch nylon spacers and mount them between the large discs. You
should drill 3 holes in a triangle patern and use 3 nylon bolts and
nuts. This will ensure that the ends plates do not move around on
you. You can mount this antenna on a mast by making some type of
bracket for support.
(Just try to put the bracket by the
mount where the coax/gamma is so that the mount should not affect
the antenna preformance.)
To match the antenna simply move
the gamma around a few times (move it in small increments is
really tough). Once you get the S.W.R. down below 3:1 then move
the small disc by loosening the nut and turning the small disc.
(AGAIN, move it in small increments)
Many thanks to the late Robert
Cook, WB2OHP for the endless hours of advice, help and lots of radio
checks.
He was the person who introduced me to "The Magic Band"
- Thanks Bob.
Editors note:
Due to the
infinite wisdom of AOL.com, many if not all of the personal websites
that were hosted by them were shutdown permanently with little
or no warning!
Christopher's website that contained these
projects was one of them, resulting in dead links to his url
at: http://members.aol.com/n2kbk/6m.html
We are happy to maintain his projects on
Hamuniverse.com.
Thanks Christopher...no thanks AOL......73,
N4UJW
