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David
I have had good success with a vertical wire of whip that is longer that a 1/4 wave on the lowest frequency with a variable capacitor at the base for tuning. I use a sectional military vehicle whip that is about 20' long mounted on a wooden broom handle that is pushed into the ground. The capacitor is connected between the centre of the coaxial feed and the bottom of the whip. Then it is just a case of connecting a couple of radials for the band that you want to work and tuning the cap for minimum VSWR. I have worked all over the world on the higher bands using my FT-817 with 5W. it takes only a couple of minutes to set up and is very efficient. The whole antenna weighs about a pound and will fit inside a rucksack. I have used it with 100W even with a receiving capacitor, as the cap is at a low voltage point there is no worry of flashover. If you want more information please email me and I will send you a picture. Jon G2FHF David B. Thomas wrote: For portable operation in the 14-30 MHz range, I use a small, handheld transmitting loop. Here is a web page describing it and how to build one from inexpensive materials. The page also links to other pages with good information on loops. http://dt.prohosting.com/hacks/antenna/magloop.html I chose the loop because it is actually possible to operate while walking around. Obviously if you are able to erect a larger antenna at your operating site, you would be able to get better performance. My loop is about 30% efficient at 14 MHz, theoretically delivering about one S-unit less than a half wave dipole. David http://www.qrz.com/n5izu |
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