Figure: Plenty of room for upward mobility of the loop
A while ago I planted a trap vertical in amoungst my little back yard “forest” of trees. It works, with patience, to grab a little DX, and the occasional local contact as well. But the noise level observed, when using the vertical, is pretty terrible. Typically it runs around S6 -S7 on the Omni’s S meter, meaning that a potential QSO requires a signal that’s much stronger than say – S1. I don’t have a tower, and am not sure if I want to tempt the locals into action by erecting one. Reconsidering my situation, I realized an obvious fact about my landscape. Indeed, I have around twenty towers on my lot in the 70 – 90 ft range. Why am I not using them? I grabbed one of the ARRL antenna manuals and looked for a candidate scheme to lace up my trees. After all, it IS the christmas season.
I settled on a loop, and cut it for twenty meters. Yes – it’s much more efficient to cut a loop for 80 or 40 meters since it can be utilized on all harmonics. But, I happened to have a nice spool of 100′ of #10 gauge steel primary wire in my junk box. I cut a section of RG6U as per the formula (L = 246 * V/ f (MHz) per the ARRL Antenna handbook) for making a coaxial transformer via a RG6U/RG213U combination for impedance matching to the high impedance loop – and then ran off a 72′ length of the steel wire for the loop itself. “V” is the velocity factor of the cable. About an hour and a half later, two of my trees were being utilized as proper “towers”.
I had used loops in the past, and they always had been favored antennas, but had not used a vertical loop in the recent past. I do have an 80 meter loop, but it’s a horizontal affair. Quickly, I re-remembered just how nice and quiet loops can be. The vertical’s S7 noise level was now transformed to an S1 noise level. Suddenly, I was working all kinds of QRP QSOs. It’s much more pleasant to work an S3 signal on an S1 noise background than it is to work an S6 signal on an S6 noise background. It’s like they say: the antenna counts as much as or more than the power (that I could reasonable run at this QTH). So, try a loop if you (like me) have forgotten how soothing they are to the ears.
The #10 gauge steel is not something I’d ordinarily use, due to the skin effect / impedance issues that are inherent in it. But, for higher impedance antennas like loops, the steel works just fine. It’s strong enough for the hurricanes that like to rip through this area occasionally. My loop is only ten feet higher than ground level on the bottom, about twelve feet higher than that on the sides, and about 24 feet wide. So, it’s a bit of a squashed loop. Loops have ground losses when so close to the ground, the same as verticals. In the picture, one can see that I have a lot of room for upward mobility in the trees. So, that’ll be done eventually, when I order a new launcher (for the life of me, I can’t find the old one). The loop as it is was done with a 24 ft ladder, which is NOT the recommended way to climb a tree!
So, transmitted signals are still a bit muted for me, pending the lifting of the loop. But, the reception is fine, and so very quiet. A recommended aerial by my account. Try one. Maybe even for POTA and such, a loop might be useful.