This antenna is basically one half of a full wave loop held up by a single support, over a counterpoise wire laying on the ground with ground rods at each end to complete the loop by mirror image, and fed at the close end for vertical polarization with a 4:1 balun for an easy match for the tuner. A pdf doc can be emailed to anyone requesting it.
Back in the 1990s when I lived in NNJ on a small lot in dense suburbs I had a pretty compact antenna system for 160m and started operating the ARRL 160m contest. I made antenna improvements and tracked them with contest results. Before long I was also given the opportunity to guest op at several stations with larger and more elaborate 160m antennas than mine. In reference to the experience gained operating a number of different antennas on 160m my conclusions for this particular simple antenna are as follows:
1. Very Quiet Antenna – Hears better than most other stations hear.
2. Only requires a single support 35 to 40 feet high.
3. Requires 2 ground rods (8 feet long), one at each end, and a counterpoise wire laying on the ground between them.
4. Antenna is Grounded from Lightning.
5. Requires a 4:1 Balun for feeding at the closest end, to match to inexpensive RG-6 coax feedline running to the shack, and is an easy match for a tuner.
6. Handles 1 KW power – if the balun is up to the task (mine seems to be).
7. Can work both DX and local with this antenna. Works to Europe, California, Texas, Florida, as well as in between. It really doesn’t seem very directional.
8. This single transceiving antenna performs at least as well as many typically installed separate transmit and receive antennas – by eliminating noise coupling from the noisy transmit antenna situated too close to the quiet receive antenna(s).
9. This antenna outperforms an inverted vee that would fit in exactly the same space, and also a much larger horizontal loop 540 feet around.
10. This simple antenna can be outperformed by more elaborate antenna systems including a good vertical or inverted L with many radials for transmitting, spaced over 500 feet from an array of switched directional receive-only antennas with a preamplifier and incorporating receiver protection during transmit.
73, Chris WB2VVV
Chris: Neat antenna and glad you included the diagram. There are always folks looking for ideas on simple 160 antennas. And this one is pretty simple. But a proven performer. Good job. As an advocate for 160 operating…. contests and daily…..anything that advances the art of Top Band QRV-ness is a good thing. And you have moved the ball. Kudos.
Itis truly amazing how many signals one hears on 160 during the TB contests. And with good signals. Everyone you work does not have a super duper antenna. As you know, you can be quite successful on Top Band with this and similar antennas.
TNX for sharing! 73.
Agreed, on simple antenna — quite interesting! And very quiet on the low bands is an excellent feature. The roughly 260 ft of space needed for it may be one of the few downsides to it for us land-challenged suburban dwellers ;^( Thanks for the details Chris. 73 de W1WBB (100′ x 200′ lot)!
Agreed – seems like a simple & effect low band antenna.
Question – you have antenna elements going from 40′ to ground level, including 260′ lying on the ground. At High Power, if someone – some child – walks into/on those elements, how much of a shock would they get? Shock for Low Power?
If I “bribed” my two neighbors to let an antenna like this extend through their backyards, I’d have to assure them its safe.
thx &73,
Mike
NG1M
Mike,
That’s an interesting question. I used black #14 THNN insulated wire on the ground because I had it on hand. The insulation is two layer, clear on top of black, and rated for 600 Volts. I cannot even find it on the ground in that field after only a couple years of being there. When I had a top loaded vertical at another home I had around 600′ of ground radials of the same exact kind of wire that I laid out right on the lawn and held those radials down with lots of home-made staples made from the white coat hangers that the laundry service put my pressed/starched shirts on. Those radials also “disappeared” in a shorter matter of months due to frequent mowing. During the time they were visible on the ground the insulation was intact and I would think provided substantial shock protection.
Every wire antenna has higher voltage nodes and higher current nodes along its length, and the voltage level of the potential electrical shock would absolutely depend upon where along the antenna’s length you are measuring, and also whether the insulation had broken down. There is also a ground rod at each end of this length of wire that lays on the ground. OTOH the largest RF field that is transmitted by an antenna is from the part of the antenna with the higher current node (versus the higher voltage node). The low bands like 1.8 MHz are from an MPE (Maximum Permissible Exposure) standpoint the safest of our bands from an exposure standpoint as the wavelength is so very large (540′) and a human is so very tiny by comparison that very little RF is absorbed. The MPE charts that show MPE by frequency show that the most sensitive area of the spectrum for absorption in humans and thus the most restrictive MPE limit is at VHF where a wavelength is about the length of a human. A former colleague of mine who was a Health Physicist at Bell Labs used to describe MPE limits as following the through-you, in-you, off-you rule. At low frequencies the RF goes right through-you because the wavelength is so large and you are so small. At VHF more of the RF goes in-you and causes the most heating which is why the MPE limit is the most restrictive, because you are pretty resonant at VHF. At UHF and Microwaves the RF tends to scatter off-you because you are so large relative to the tiny wavelengths. The MPE limits are set basically by the potential to heat a person, which is the only measurable effect that has been found for RF as it is in the non-ionizing part of the spectrum. The MPE limits are in fact set 100 times lower than the smallest heating effect that can be measured with the most sensitive measuring equipment.
In the end, I would use insulated wire and home-made staples to get it out of sight as soon as possible to avoid attracting the curiosity of a child because you don’t really know where along the wire’s length they’re going to be attracted to, and I would say it’s insulated wire plus it’s grounded at both ends. I would think you could ground it in even more places if you wanted to with no effect on the performance of anything but a lawn mower blade that finds a ground rod. It is also certainly feasible to make the single center support point higher to reduce the length of the counterpoise wire between the ground rods. 73, Chris WB2VVV