Re: CCW Inverted-U antenna
David Coles M0IDF
Hi Chaps - I have two friends who each have the inverted U from Chris. They do work very well on 20 mtrs but as you drop down to Top band the efficiency diminishes rapidly. If you look at the model Chris refers to I seem to recall an efficiency of around 1% - Chrsi pls correct me if I'm wrong.
I did play around a lot in the model and Chris's dimensions are the best compromise I found for angle of radiation - you do increase efficiency by increasing the length of the top but it does do weird thing to the radiation pattern.
In spite of the low efficiency on Top Band it does get out on local ground wave. I've attached a video below of me chatting to a chum running about 10 watts around 6 miles away - note mode is AM. He was with another chum who ran around 2 watts of AM from an 817 on battery and I could hear him fine. My antenna is a short loaded inverted L with a raised tuned c/poise.
I set one up at the QTH of a friend. Unfortunately he had horrendous noise levels. The Inverted U did help but it was tough going on Top Band from there. It worked very well on 20mtrs under very flat conditions.
Here's a link to the video - hopefully of interest (Note you don't need to download the video to view. Just click the icon at the lower left and select play)