halfsquare

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Half Square article by Rudy Severns, N6LF
a very interesting article

My Half Square Antennas That I Built and Used At My Montana QTH :

This article explains about my half square antennas. In 1982 I built a 160 meter, 140 foot tall vertical with 40 feet of top loading, I made the antenna out of irrigation pipe and guyed it with 3/8 polyrope. Electrically it appeared as a half wave, had no radials as it needed none, as the feed impedance of a end fed halfwave was approching infinity. I think this was the best transmitting antenna I ever had for 160 meters. The vertical was great but was poor for a receiving antenna it was very bad, had 10 db over 9 or more. I was lucky to live in the middle of a bunch of wheat fields and during the winter months I could run 1 wave length beverages for receive, I had 8 of them pointing at the 8 compass points. This was a very good 160 meter system. I was lucky enough to get 100 countries by 1986 using that system. The place we living at was a rental and when we had the chance we starting buying a home, but only had 2 acres. I put up the vertical again but had no place for beverage ants. About a year later we had a bad winter storm here winds 60-100 mph for a week, the big vertical went down after three days. I started looking for a better ant for 160 that would fit on my place. I had been off the air for a while as was busy working and with no good ants lost interest. I found an article by Rudy Severns, N6LF on the internet and it was about the half square. This ant is just about the same as a bob tail curtain, the same person invented them both the half square first but people thought it was too simple, so he added a third vertical to the half square and called it a bob tail curtain. It looked like would fit on my place and with his dimensions it only needed to be up 60 feet, which I could make out of pieces of the big vertical which was ruined. I made one running nw to se, as this antenna is bi-directional, so this would work good for me to eu and south pacific. I when I go it up the band was dead for dx, which is normal for 160 for this area. I got it up and tuned with a good match, it scared me, as the noise was very low, but a good friend of mine, WA7OFH Bob Miles told me he had a bob tail curtain up in the 60's and he had the same thing, it was so quiet he didn't think it was any good, when the eu starting coming in he was so surprised at how load they were. I listen every night to see if I could hear and dx, then on Jan 22 2008, I started hearing a CW cq with the call J5C, I thought this was a pirate as I had been off the air and didn't no this type of a call was real, but started hearing stations calling him but he didn't answer any one, so I put call out and he called me and gave me a 599 report, I gave him a 449. I got on line and found out this was a dx expedition to Guinea-Bissau in Africa. Well that was what I needed to know, it worked and only a s1-s3 noise level using my drake c lines. This antenna is very quiet as it has a take angle of less then 10 degrees, it dose not hear man made noise as its a very high 45-90 degrees. This was my first one, I actually put it between two trees, one on my land the other tree on a neighbors land, but could only use it for that winter as they were building a house there the next summer, so in the spring I build two of them using 3 60 foot poles, the feed point comes off the one in the center to a common tuning network which I have a relay switch able from my shack, one for EU/S Pacific the other one for JA/S Africa . I built one for 40 meters, full sized, between two if my guy cables for my 100 foot tower, it is for EU/S Pacific, was going to put one for JA/S Africa but didn't get that done yet. Tuning the antennas is showed on the included an article by Rudy Severns, N6LF, Fig 10 (A) is the one for my 160 meters ants, Fig 10 (C) is what I am using for the 40 meters. the open wire length is a odd quarter wave length, and the antenna end of that open wire one side goes to the ant the other side of the open wire is connected to nothing. Think about it, the impedance of and end fed full ant is infinity so you don't to tie other end of the wire to anything as long as it is a odd number of a quarter wave length then one end will be very high impedance and the other end very low impedance. I am using a Johnson KW matchbox for 40 meters, balanced wire fed.

Below you can see the 140 foot vertical I made in Montana.

CLICK ON IT TO SEE IT LARGER

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