IW5EDI Simone - Ham-Radio
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Coaxial Dipole Antenna by WB4CPO
Posted: 24 Aug 2018 01:13 AM PDT
http://www.iw5edi.com/ham-radio/2815...enna-by-wb4cpo
A coax atenna project by WB4CPO from the late 80sĀ* that can be considered a
double bazooka antenna.
Type of coax needed RC 58/U or RC 8/U. RC 58/U is the best.
Use the same type coax for antenna and feed line.
Maxium legal power can be used on the RG 58/U without fear of feed line
breakdown.
80 meter example:
Start with 128 ft of coax and make center reference point. Measure from
center reference point out each way for a distance of 30 ft 6 in. Solder
the inner conductor to the shield at both points. This forms the 52 ohm
matching balun. Waterproof both joints well. Next, at both ends of the
antenna, short the center conductor to the shield but do not waterproof
until after trimming for tuning purposes.
At the center reference point, remove one inch of the vinyl jacket (1/2 in
each side of center).
Cut the shield in the center all the way around the coax.
DO NOT CUT THE INSULATION OR CENTER CONDUCTED.
Connect the feed line to the shield leads, one shield lead to the center
conductor of the feed line and the other shield lead to the shield of the
feed line.
Waterproof well and mount on a 4 in x 4 in piece of plexiglass to hang from
outrigger up on tower.
For 75-80 meters the feed line lengths should be 57 ft, 87 ft, or 103 ft.
Separate feed lines must be used for each band.
In summary, the advantages of this antenna a
Broad bandwidth: Unaffected by environment
Positive gain over a common dipole
Greatly attenuate harmonics
Decreases static charge build-up
Essentially non-directional
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