6
METER HALO ANTENNA DESIGN
April 28th, 2002, By Steve KB1DIG
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Something a little more advanced. Always fun to
try out
new bands.
This halo is made with a true Gamma Section this time and is
fashioned
from aluminum.
Most of the parts are leftovers from old car projects.
The best part is it's omnidirectional!
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The 3/8" fuel-line I used came from Summit
Racing Equipment: http://store.summitracing.com #SUM-G2538,
and a 25' section costs only about $20.oo.
 Frank NG1I and Steve
N1TYH used aluminum fuel line from a NAPA
auto parts supply store. http://webpages.charter.net/maclamb/6m_halo.htm
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Some of the mods I came up with were:
- Welded the elements to the aluminum plate with some of
that "Alumaloy"
stuff advertised on television.
Alumaloy Sample
auction
1/10
pound or 2 rods of alumaloy aluminum repair rods.
Go to
eBay: http://www.ebay.com/
Key words
for search: (SAMPLE) Aluminum REPAIR Rods ALUMALOY
- I drilled a small hole in one of the elements to allow
condensation
to evaporate.
- Capped off the end of the gamma arm with a plug to keep
the weather
out. The plug was an automotive type used to block off a
PCV
line from a carburetor.
- After mounting horizontally to a 10' mast I added a
support system
made from 2 thin 3' fiberglass rods and some wire-ties.
- Also, remember
to hot-glue the wire-ties to the fiberglass rod.
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Both 54" elements are bolted and welded to the mounting
plate.
Use galvanized or some other type of corrosion resistant bolts.
The
size of the bolts is not so important other then that they fit snugly
into
the ends of the 3/8" fule-line and hold the elements in place while
welding
the elements to the mounting plate.
This "Alumalloy" product is great
for this purpose and is more like soldering than welding.
After the
2 elements are welded, leave the 2 bolts in place for added support. |
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The so-239 connector is pop-riveted to the mounting
plate.
Face the pop-rivets out and away from the gamma section.
Cut back
and expose about 1/4" of the center conductor of the RG-8 section for
soldering
to so-239 connector. |
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Position the 1" wide aluminum bracket on the Gamma arm,
inward about
3 1/2".
Expose about 3" of the RG-8 coax center section.
This
is just a starting point for matching this antenna.
I was lucky and
didn't need to make any further adjustment for lowering the SWR.
The SWR on this design seen here, just the way it is, was 1.2 to 1 at
50.125Mhz. |
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This halo design is intended to be mounted parallel to the
ground.
It should work well for base or mobile operation.
I presently use
this antenna at my home QTH and it has proven itself to be quite
successful
for SSB work. It is presently up on the roof, mounted to a 10'
mast
section in a 3' tripod stand.
It can also be modified to work on
the FM portion of the 6-meter band by shortening the length of the 2
main
elements a little at a time. I have not done this. No
change
to the gamma arm will be required if this antenna is altered for
6-meter
FM. |
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