40m delta loop antenna
With age I have learned to couple my dreams with realities. I no longer shoot for the stars. I prefer to shoot for targets I can easily hit. Unfortunately I do not have any pictures, so you will just have to look at my drawings. If you cut the antenna too short, you can just add a loop of wire. If you are installing it for permanent use, this is not important. Here are some recommendations / estimates of overall length depending on resonant frequency:. NOTE: This is not a plug-n-play antenna. If you want it to work properly, you will need a means of measuring SWR, some trial and error, a little patience and at least half-a-brain to build this. The insulator shown directly on the pole at the 2m level is for mechanical reasons. Secure the insulator to the pole, and then pass the horizontal leg through the insulator, reducing sag in the horizontal leg. Local QRM is weaker (usually a few S-Units), thus less QRM. Feedpoint was placed 1/4 wl down the pole (note: I did not consider the velocity factor here, but it is not very critical if it is off by a foot or so). If you are installing it for permanent use, this is not important. The pole should be about 12m high (minimum 11m). (39'4". The antenna will have an impedance between 90Ω and 100Ω. A quarter wavelength matching stub of 75 Ohm coax will provide a good match to 50Ω. Use RG-59 for up to 500w. If you want to run more power, use RG-11. Notice I inserted an additional insulator in the horizontal leg, near one corner. Each time I changed my QTH, I had to re-adjust the length of the jumper. I just let the jumper wire hang down. For permanent use, you may leave this out. one side from the insulator and then roll the antenna as a single wire. The length of the diagonal is not very critical and may be adjusted to help find a better fit in the space available, but the distance from the feedpoint to the top should be. Do NOT place too much focus on the exact lengths shown in the drawing. I first became aware of this antenna from an article written by DL1BU (SK) in CQDL magazine, April issue, 1979, page 154. I built the antenna immediately and fell in love with it. It is low cost, easy to build and easy to bring into resonance. Note, I use the term "resonance" loosely here. What I actually mean is it is easy to tune the frequency of minimum SWR to anywhere you please, because it is broad-banded so you only have to get close. and leave it hanging from the insulator. That is usually enough to bring it into resonance on the desired frequency. For home use, the JUMPER is not necessary, but if you are using this portable, you will be adjusting the length a lot and this makes it easy. REASON: See Sidebar on "LENGTHS" at the bottom of this section. apex 1m below the top of pole (for stability). '). Higher is better, but then you will have to re-adjust the total length for resonance. Advantages over a full size quarterwave vertical with a good radial network:.