Wire Antennas

For years, my main antenna was the longest piece of wire I could string out the window. I tuned it using an LC tuner, which worked OK most of the time. (The piece of wire I had strung out the window of the Priory in Stellenbosch was hi-Z on 21MHz, the capacitor arced at anything more than 2W output, but I still managed to work South America).

Wire antennas give the highest price/performance ratio of all.

I came across a design for an "all wave" dipole fed with two parallel sections of RG-58 coax. Each side of the dipole is 27 feet long, and so is the feedline. WB1GFH states that this antenna / feedline combo is a bad idea, even though it worked well enough for me. (A 40m G5RV uses about half this feedline length.)

In general,
Wavelength (in meters) λ = 300/f(MHz)

When it comes to antenna lengths, however, there are various factors that influence things, with the result that the following equations are more common :

Dipole : L = 143/f(MHz) or L = kλ/2, k=0.953
Inverted V : L = 148/f(MHz) or L = kλ/2, k=0.987

NEC http://users.tpg.com.au/users/ldbutler/SingleCoilZMatch.htm http://ac6v.com/antprojects.htm http://www.w5gi.com/mysteryantenna.htm

Well, a web search turned up W5DXP's page where he explains the whole thing with a graph.

54 ft dipole is (54/936)*14.1 = 0.8 wavelengths, match = 0.3

Antenna Tuner

• Slim Jim
• W1CG 4:1 Balun
• N1HFX 4:1 Balun
• W8AR High Power Antenna Tuner.
• Amidon states that a balun wound on an FT-240-61 ferrite core can handle a kilowatt.

Baluns

K0JD reports that he's running 50 watts through a balun consisting of three turns on an Amidon BN-43-3312 core. This core is 19.5 x 9.5 x 25.5 mm with two 5mm holes through it -- tiny by my standards, and I certainly would not have thought that it would handle 50 watts.