June 2, 2007
A 20-meter QRP gain antenna
Genesee Mountain at 8,000 feet west of Denver, Colorado. First attempt to test the new antenna.
Radio is my Yaesu FT-817 running 5 watts
Radio is my Yaesu FT-817 running 5 watts
Three halfwave verticals phased with homebrew ladder line
Those fluffy white clouds became
thunderheads in a matter of minutes, forcing a cancellation of testing
after only one contact. Before pulling down the antennas, I heard
Germany, Italy, and England stations.Here are some photos detailing how I put it together.
$1.00 bamboo place mat will become the spacers for ladder line
Each 12" bamboo stick was cut to make 4" spacers. The ends are wrapped in electrical tape to prevent splitting when drilled.
Making open wire feedline in the front yard. I Super-glued the spacers to the wire
Every fifth spacer has a hanger to help support the feed line
Center pole showing feed point, feedline, and rope to support feedline.
I found a good match with the homebrew L/C tuner
Diagram of phased antenna layout
The antenna spacing between each element
should be 492/freq, but is limited to the velocity factor of the
1/2-wave feedline. I used 24-ga. stranded insulated wire instead of
bare wire. The actual vf worked out to just under 95%. Next time I will
use uninsulated wire!
Each antenna was cut to 32 feet in length. Again, the insulation, as well as the fiberglass pole it rests against, reduced the velocity factor as measured into the matching unit and MFJ antenna analyzer.
Cost:
$0.46 wire - I bought a 5,000-foot roll of #24 wire at a hamfest for $10 which works out to 2/10 of a cent per foot.
$1.00 bamboo - at the local Dollar Store
$1.46 total - I already had the matching unit, support rope, Super Glue, three MFJ fiberglass poles, and PVC bases from earlier projects.
Credit for the antenna concept goes to the ARRL Antenna Handbook 19th edition, page 8-40. Thanks to John Marshall, KU4AF for pointing me in the right direction on the phasing issues.
I will have to wait for a day with no lightning nearby to trial the antenna.
Jake, NØLX
Each antenna was cut to 32 feet in length. Again, the insulation, as well as the fiberglass pole it rests against, reduced the velocity factor as measured into the matching unit and MFJ antenna analyzer.
Cost:
$0.46 wire - I bought a 5,000-foot roll of #24 wire at a hamfest for $10 which works out to 2/10 of a cent per foot.
$1.00 bamboo - at the local Dollar Store
$1.46 total - I already had the matching unit, support rope, Super Glue, three MFJ fiberglass poles, and PVC bases from earlier projects.
Credit for the antenna concept goes to the ARRL Antenna Handbook 19th edition, page 8-40. Thanks to John Marshall, KU4AF for pointing me in the right direction on the phasing issues.
I will have to wait for a day with no lightning nearby to trial the antenna.
Jake, NØLX
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