The "Wye", a 3-Wire Ground-Plane Antenna
So, here you sit. You just got a new radio, or the urge to run on a band that you haven't used your old radio on before. So you grab your "MEGA-RADIO" catalog, open it to the "ANTENNA" section, and just about CHOKE when you see the prices on the antlers for the band of interest.
So, what is the cheap, er, frugal Ham to do? How about a ground-plane antenna? "Sure", you say, "Aluminum tubing just grows on the trees around here..." Maybe not, but good old #14 house wire is inexpensive, and readily available. What you need to do is to simplify the Ground-Plane (GP) antenna.
Looking at the GP, it is basically a 1/4-wave radiator, working against a "ground-plane". the ground-plane is an elevated counterpoise, which provides an electrical "image" of the radiating element. The simplest form of the GP would be a vertical element, with a 1/4-wave wire extending out at a 90-degree angle from the feedpoint. This used to be shown in the "Radio Amateur's Handbook" as the "30 Up & 30 Out". It was a 30 foot vertical, mounted on the roof, with a single wire extending out 30 feet, and was fed with 300-ohm ribbon, or ladder line. Despite the simplicity, this is an effective antler, and is still a viable one today.
The next step up is the "Wye", a 3-wire GP. In this configuration, the radiating element is hung from the eaves, (if high enough), or a tree branch. The radials consist of 2 wires connected to the braid on the coax cable, and pulled out & down, forming an upside-down "Y". In its simplest version, on VHF, the wires can be solid #10 or #12, with the wires soldered directly to a chassis-type coax connector. Zack, KH6CP had just such an antenna in "QST" in 1992 or 1993, but I can't find the exact month right now. In "Ham Radio", back about 1985, W1JR had a 20 Meter version published, and Doug, W1FB has a 30 Meter version in his "Antenna Notebook". Nothing really new, but a good idea is ALWAYS worth repeating.
|
Frequency |
Radiator |
Radial |
|
7.1 MHz |
33.0' |
34.7' |
|
10.1 MHz |
23.2' |
24.4' |
|
14.2 MHz |
16.5' |
17.3' |
|
18.1 MHz |
12.9' |
13.6' |
|
21.2 MHz |
11.0' |
11.6' |
|
24.9 MHz |
9.4' |
9.9' |
|
28.4 MHz |
8.3' |
8.7' |
|
29.4 MHz |
8.0' |
8.4' |
|
52.5 MHz |
53.5" |
56.2" |
|
146.0 MHz |
19.2" |
20.2" |
CHARTS & FORMULAS
You can't have anything on antlers without a chart or three, and formulas are needed to beef up the information, so here are some dimensions and formulas for the "Wye", for 40 - 2 Meters:
Radiator(ft) = 234/F(MHz)
Radial(ft) = 246/F(MHz)