Simple Antennas for the Amateur Radio Operator–a continuing series


A simple multi-band loop antenna for 40 through 10 meters

Post #191

Every once in a while, I stop by eham.net (http://www.eham.net) to collect a few antenna ideas and check out the classified ads for used rigs, connectors, and other useful stuff for my junk box.  Eham also has an interesting forum section, which discusses everything from antennas and homebrewing to CC&Rs and TVI.  I’ve picked up many ideas from this useful site.

Today was no exception.  When I brought up the website, the first article I saw was “Getting on the Air”–the making of a multi-band loop by Lane Zeller, KU7I (JH1JCM).  Lane is serving with the U.S. Navy in Japan and was looking for a way to get on the air from his government housing on the base.  He had a 23-foot by 38-foot open backyard that he was able to squeeze in a 12-foot high, 118-foot loop.  For supports he used pvc poles pushed into some scrap steel pipe he found nearby.  He feed the loop with 300-ohm tv twin lead, which led into an outboard MFJ tuner and then into his Yaesu FT-890.  Despite the antenna’s low elevation, he was able to work a variety of stations from 40 to  10 meters, including Russia, VK, ZL, and Washington State.   Lane has included several excellent photographs of his project.  From what I gather from his article, the financial outlay for this project was minimal.  He seems to enjoy the flexibility and good performance of this loop, which is just a bit short for 40-meters.  His outboard tuner apparently can handle the mismatch without any problem.  Another triumph of creativity over space restrictions.  The article is well-written and may give you some new ideas when it comes to restricted space antennas.

Like Lane, I’m a firm believer in loops.  They are quiet, unobstrusive if they are mounted properly, and multi-band if you use 300-ohm tv twin lead or 450-ohm ladder line.  My under-the-house 40 meter loop and the 20-meter loop under my garage roof are fed wtih 450-ohm ladder line and perform well with the Drake MN-4 tuner and a 4:1 balun.  Although I use these loops primarily for interisland contacts and afternoon nets, I find them useful on the higher HF bands as well.  My loops are made to be emergency NVIS (near vertical incident skywave) antennas designed for a range of 200 to 300 miles, which covers all the major Hawaiian Islands.  Sometimes propagation is favorable and I can get a good 599 signal into the U.S. mainland from my Hawaii Island qth (a distance of 2,100 miles or so to Southern California).  I was glad to read that Lane is getting some good DX out of his homebrew loop in Japan.

Perhaps Lane’s horizontal loop can give you a push in the right direction.  Even at a low height, loops can cover quite a bit of territory, especially if you’re into local or statewide nets.  In my neighborhood, loops and short verticals seem to work best.  As mentioned previously, my backyard is small and there are several homes within a stone’s throw of my qth.  Add to this mix a marginal area for television and radio reception and nearby power lines and you have the recipe for antennas which blend into the background and don’t add to the already high noise level along the Hamakua Coast.  The salt air from the nearby ocean creates havoc with utility lines–you can see the corona discharge coming off some of the huge insulators that support the high voltage lines.  The Hawaii Electric Light Company tries its best to wash the salt deposits off the lines, but nature rules in the end, and the noise soon returns. Although I get better DX with my various vertical and inverted vee antennas, they tend to be susceptible to powerline noise generated by the corona discharge from salt-laden insulators on the utility poles.  So, my low level horizontal loops have the edge when it comes to noise.

If you have the time, may I recommend the antenna forum in eham.net?  The forum contains useful tips on how to improve the antenna you do have and suggests a variety of approaches to antenna problems.

Take care as we enter a new week. As always, thank you for dropping by.

Aloha es 73 de KH6JRM

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