Wire: Wire antennas can be made of virtually any type of wire you have on hand. I have found that copper wire works a little better than aluminum wire. I prefer stranded copper wire to solid copper. I have made both dipoles and inverted Vs from just about every type of wire including Zip Cord, phone wire, thin 25-gauge wire and romax house wiring. The great thing about wire antennas is that you can usually scrounge around and find the wire.
Insulators: I have used many different things for insulators. You can use PCV pipe cut in half (1.5 or thicker PCV, about 3 to 4 long cut in half and drill holes for the wire and rope to feed thru), Ceramic insulators (these work the best, I find these at Hamfests usually under tables attached to stay wire), Plastic insulators (Also at Hamfests) and nylon rope. For the center you can use the same items as above or you can fashion one using a 1 PVC tee, three 1 PCV caps, and an SO-239 connector.
Cutting the wire: When you cut the Dipole or Inverted V to the band you wish to use it on, always add about 16 of wire. You will need the extra to wrap the wire around the insulator and it is easier to shorten an antenna than it is to lengthen it.
The Dipole is a very simple and inexpensive antenna to make. A Dipole is a resonant half wave wire antenna. The theoretical half wave length may be calculated using the following formula 150/f(Mhz) meters or 492/f(Mhz) feet. This formula is all well and good in theory but as with most theories it needs to be massaged a little bit. I prefer to use formula 468/f (Mhz) feet (see chart below). This formula is much more real world and has turned out some great antennas for me.
Lengths of a half wave
Diploes
|
Frequency (Mhz) |
Length (feet) |
|
1.850 |
252 11 |
|
1.950 |
240 |
|
3.550 |
131 10 |
|
3.750 |
124 9 |
|
7.050 |
66 4 |
|
10.100 |
46 4 |
|
14.100 |
33 2 |
|
14.250 |
32 10 |
|
18.100 |
25 10 |
|
21.100 |
22 2 |
|
21.300 |
21 11 |
|
24.940 |
18 11 |
|
28.100 |
16 8 |
|
28.500 |
16 5 |
|
29.00 |
16 1 |
|
29.500 |
16 10 |
Feed line: Dipoles can be feed with 50 Ohm coax, any of the light weight RG type coax can be used for example RG-58, RG-59, RG-6 and RG-8X. It is better to use the lighter weight coax for runs less than 200 feet.
Antenna Height: The optimum height for a dipole is a half wavelength above the ground. This is very easy on most of the bands above 20 meters (32 feet) but very hard to do in real life for 160 meters (252). The best advise I can give is put the dipole up as high as possible.