80 Meter Half Square Antennas by N4DJ
In order to work DX you need an antenna with low angle radiation. The more power you can focus at the low angles the better your DX results will be.
The problem with horizontal antennas on 80 meters is that you have to have them really high to get low angle radiation. An antenna only a half wavelength high has most of its radiation at 30 degrees. Having the maximum radiation at 15 degrees would be much better. With a 80 Meter dipole to even get the maximum down to 30 degrees you need the dipole up at about 130 feet.
Vertical antennas, in general, are not dependent on height above ground to obtain a low angle of radiation. The quality of the ground under and around the vertical is important. Another factor we need to be concerned with in the performance of a vertical is that of a radial system to reduce the ground loss. In most verticals the ground makes up half the antenna and unless you have a good radial system you can lose a lot of your power in the ground resistance. One way around this is to use a vertical antenna that does not require the ground to make up half the antenna. While a 60 foot vertical on 80 requires a good radial system, a full size vertical dipole does not. Of course, a full size vertical dipole requires a support over 120 foot high! I have found, what I think is a better way to go on the low bands.
A Half Square antenna solves many of the problems associated with needing excessive height and excessive radial systems on 80 meters. While full size half squares on 80 requires about 75 feet in height, bent versions can easily be constructed with minimal reduction in gain from the full size version and still be better than a dipole at 60 or 120 feet.The gain at 15 degrees for the full size half square (top at 75 feet) is 6.2 dBi, while the bent half square (only 55 feet high) is 5.8 dBi. The bent half square is only about .6 dB down from the full size version.
At an elevation angle of 15 degrees the bent half square is actually better than the dipole at 130 feet!
I used this antenna on 80 meters for just over 7 years. The maximum height was 55 feet. The ends were only bent in about 15 feet. In my case hanging the half square between two pine trees allowed me to have an antenna that was probably better for DX than a dipole at 120 feet. Performance of this antenna was exceptional. I worked over 140 countries with it on 80 meters. I am not 100% sure, but I think it should out perform a "4 Square" array in two directions. However the 4 square has the advantage of being unidirectional and being able to switch the pattern. It is also a lot more complicated and involves extensive radial systems.
How do these antennas stack up against a full size quarter wave vertical on 80 meters? Well I always thought that a full size vertical would be a great antenna. I have had a couple of 70 foot towers shunt fed for 80 meters and also with extensions out the top to get me to a physical height of about 108 to 110 feet. With some top loading I had about the equivalent of a quarter wave vertical on 160. I have also operated with 135 foot verticals held up by balloons. These full size verticals were good antennas at the time. However, I think it is safe to say that a good quarter wave vertical will probably have a gain less than 1 dBi , if that high. Of course the pattern should be omni directional. That is both good and bad. Good because it covers all directions and no nulls in the pattern and bad because it covers all directions with no nulls in the pattern!
The ultimate in vertical performance would be if it were over salt water.
Although the 2:1 SWR bandwidth is only about 80 kHz, operating with a high SWR does not seem to affect the performance at all. If the antenna were to be fed at the bottom of one of the vertical legs, such would not be the case.
No doubt that arrays of two or more full size quarter wave verticals will out perform the bent half square, but the effort and expense to install such an array is usually beyond the reach of most of us. The cost of a bent half square is essentially the cost of 260 ft of wire and a few insulators, providing of course you have a couple conveniently placed tall trees! Another advantage of the half square is that it can be fed directly with coax. On my 80 meter half square I usually add and remove short extensions to the bottom of mine prior to a DX contest to adjust it for CW or SSB. For CW a I add a few feet to the lower horizontal wires to get the best SWR around 3525 and remove it for SSB so that it is resonant around 3795. I have found that it works just as well on 3795 when tuned for 3525, the SWR at the amplifier is just higher than most of us would like. However on 80 meters the coax loss is very low to start with and the additional loss due to operating off frequency with a high SWR (in my case) is about 1 dB. I figure that brings my 80 meter half square down to being only as good as a dipole at 120 feet! I can live with that.
A couple of last notes. I also put up a "bent" 160 version of the Half Square at one location and it worked fairly well. But there was some interaction with my inverted L. It turned out that having the bent 160 meter half square behind my inverted L seemed to form an array with the half square acting as a parasitic reflector. EZNEC verified that that was the case. The 160 Half square had a top wire about 250 foot long, the vertical sections were both 60 feet long with the last 60 or so feet of each side being bent in parallel to the ground about 5 or 6 foot high.
LINK TO MY HALF SQUARE VIDEO:
Preliminary modeling with EZNEC indicates that my Half Square may only be 5.7 dB down (at an elevation angle of 15 degrees) from a Quad with the bottom at 100 feet.
It appears that a good 80 meter antenna can be had with out extremely tall towers and lots of expense, however it probably will never reach the performance level of extremely high quads and Yagis!
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