Antenna Building

I’ve been slacking of late on the websites and social media while I’ve been preoccupied with several other things going on from antenna issues, health stuff, and life in general. In reference to the antenna issues I thought I’d share a few things and share a tool I came across today that you may find quite handy in your next antenna build or adjustment.

First, my OCF 80 M dipole was giving me fits. As Doug, K5BAK, and I talked about it, we agreed that it hadn’t really been right since we put it up, but we could not determine why. The problem seemed to worsen about a month ago, when it was apparent that my receive was, to be honest, crap. Stations that were rattling other speakers couldn’t be heard over the noise on my radio. This was the last straw for me and I determined that I was pulling that antenna down and getting it right.

Upon lowering the dipole and inspecting the balun, feedline, and both legs of the dipole I was unable to discern anything that stood out to me as a potential source of the problem, so I decided that I’d replace both legs altogether and eliminate the wire as a potential problem. I dug around for a while on different forums and websites looking at how others had designed their OCF dipoles from feed point location to wire size to leg height and more. Ultimately I decided that my goal was to be resonant at 3.800 mHz, so I figured out that my overall length needed to be 129.42′. The 2/3:1/3 leg formula seemed to be the most consistent and well performing, so with that in mind I wound up with a long leg that was 86′-3-3/4″ long and short leg 43′- 1-3/4″ long.

After attaching my insulators on each end, I went to the balun with 2 copper lugs and secured these to either side of the balun for my wires to connect to. I stripped about 2-1/2″ of insulation of the wire ends and looped them through each lug before soldering them making a loop around the lug with a secure connection. I pulled the balun and feedline up to approximately 35′ height then went inside to test.

Test was great. Using an MFJ-226 analyzer, I found SWR on 80, 40, & 20 Meters to be under 1.9:1 and impedence between 56-62 ohms. I’m satisfied with the results there. Now for the tool I came across today. It is an SWR calculator for dipoles and verticals by DX Commander.

SWR Calculator

It’s a quick and simple tool to use. Plug in where your dipole is currently resonant and where you want it to be resonant. It will quickly tell you whether you need to add or remove wire as well as how much. Give it a try.

73, K5RFL!

%d bloggers like this: