Antennas You Can Build
(Updated January 26, 2009)
The antennas that are in this section have been analyzed using EZNEC. The inverted L is probably the most popular antenna used for crystal sets. See how it compares to other BCB antennas. Also note that I have included antennas for the ham (an 80m beam and a beverage). Since there is a two-way category in both our active device and crystal set contests, these antennas may be of interest to you.
Examine the patterns and the impedance, and pick an antenna for your location. If you have a reference antenna that you can keep up, you can have a standard for comparison.
Here are a number of things to think about that can affect your antenna system:
–Nearby objects that absorb/reflect signals
–Poor grounding system
–Horizontal vs. vertical polarization responses
–Improper matching of the antenna to crystal set.
GROUND LOSSES: Note that each of the antennas modeled on this site also have ground losses associated with them that will subtract from the gain shown in the antenna plots.
There are a couple of types of ground losses to consider. There are the losses associated with the "near field", that is, the losses associated with the ground system that is the "other half of the antenna." You can do a lot to improve these losses, by using ground radials in conjunction with ground rods. Connecting to a well grounded copper house water system can work wonders.
Ground losses also include the losses of the ground as a medium usually associated with "far field" plots, as displayed on this site. There is not a lot you can do to improve these losses. Different types of soil reflect the radio waves better than other types. You are pretty much stuck with your soil!
ANTENNA PARTS: For stealth antennas, #18 enameled wire works well. A 500' roll of black plastic-coated #14 solid house wiring can be used for an even sturdier antenna. Insulators can be cut from clear plexi-glass, or commercial plastic or ceramic ones can be purchased.
A sling shot in combination with a fishing reel can get the antenna up to new heights. I connected the fishing reel to a sling shot with hose clamps. Use a large nut, perhaps 5/8" to shoot from the sling shot. The fishing line has to be strong enough not to break, but light enough to go far. After you shoot the nut over a tree or other support, cut the nut off and tie nylon plumb line to the fishing line. Reel the fishing line in, pulling it and then the plumb line over a tree. For an even sturdier support, you can them pull up some dark green or black parachute cord. This stuff tends to hold up pretty well in the sunlight. TARGET sells it here in 50' pieces.
Be sure to leave enough slack in the antenna so the first high wind won't destroy your work. Also, I like to short my antenna to ground when I am not using it.