I decided to construct a G5RV myself and found it was extremely easy and has offered good results.
The formula is easy too, so it makes for a fun Saturday or Sunday project.
For the wire the formula is:
492 x (n – .05) / Freq. in mHz. n = number of half wavelengths in the antenna.
A G5RV is a 3/2 wave antenna on 20m so you use 3 for n. I used 14.200 and came out with 102.2 feet.
For the matching section the formula is:
Length = 492 x Velocity Factor / Freq. in mHz
I decided to use what was immediately available which was Radio Shack ribbon wire. It has a velocity factor of .82. Again, I used 14.200 for my center frequency and obtained a length of 28.4 feet.
In case you don’t know what velocity factor is, it’s a parameter of the speed of a signal as it passes through coax. The velocity factor varies upon the quality and type of coax. See: http://en.wikipedia.org/wiki/Velocity_of_propagation
From this point it’s simple, connect the matching section to the wire. After cutting the 102.2 in half, you have two 51.1 feet legs. You can use any means to connect the wires. I used simple PVC for both the center insulator and ends insulators. For the center insulator I used some zip-ties for support of the matching section to the wire legs of the antenna. For the connection point, it’s up to you if you use a SO-239 on the end of the matching section. I have used the SO-239 and also simply connected the 50 ohm coax directly to it. Both ways work equally well.
Have had good results with the antenna. I have worked about 30-35 SSB DXCC with the homebrew version of the G5RV on 80, 40, 20, 17, and 15 meters in the past two or three months. I previously used a commercial version and it had equally good results. I am anxious to compare it with a loop antenna once I try that project again. I believe the loop will offer similar performance but a bit quieter.
Brad
AI4FO
