An easy-to-build general purpose receive only small wire loop antenna
As much as I like my coax loops, I am also quite satisfied with small loops made with wire or tubing. They have the same or better performance as the coax loops, but might require that you invest in a balun to help maintain directivity and avoid common-mode noise ingress from the feedline. If you need to null local noise yet still be able to listen to most skywave signals, these loops really perform.
The antennas described below bridge the gap between operating as a constant-current small loop (0.10 wavelength or less circumference), and intermediate-sized loop a bit larger than 0.17 wavelengths long in circumference.
If you are interested in building loops made entirely from coax cable you may want to check out my earlier project pages on that subject. It has many operational notes and other items of interest that pertain to small plain wire loops as well as to coax types.
The voltage balun was essential to help me fight common-mode noise and maintain directivity. If you don’t use a balun and have good results, you may not have much noise to deal with in the first place, or the skewed directional pattern has a null that works for you – even if it isn’t textbook. See my balun notes below.
I initially chose 14 feet since my noise problem extends up into the 40 meter band; I didn’t want the antenna to be longer than 1/10th wavelength because you start to lose your nulls with larger wavelengths of wire. I just did a quick calculation: (1005 / 7.150 * 0.10)
Note that I have since opted to use 28 feet overall, because I wanted better sensitivity on 160 and 80 meters, and now at 40 meters the 28 feet of wire still gives me a slight null – adequate enough for me to null my local noise on 40. Unfortunately I don’t have the room for a full-sized loop, so I had to wind it with two turns. See the EZNEC® antenna modeling plots below.
Here are some quick construction tips to get you up and running quickly. I’m still studying the antenna and will improve the page as time goes on.