A few weeks ago Del, W5QQ, told me about an antenna I’ve never heard of before, the Half Square. It’s a simple wire antenna, single band, with around 4.4 dBi gain (a dipole is 2.1 dBi). It is bi-directional off the sides of the antenna. It sounded quite easy to build and an interesting experiment so I threw one together this afternoon. I was hearing several stations on 15 mtrs this afternoon so I thought that would be a good band to build one for.
I found this website that gives details and a diagram for a 20 mtr version, I then scaled it for 15 mtrs.
http://www.qsl.net/ka1ddb/20meterhalfsquare.html
The two vertical sections are 1/4 wavelength and the horizontal part is 1/2 wavelength. The formula to use is 1005/4/Freq (MHz) for the vertical sections and 1005/2/Freq (MHz) for the horizontal wire. I have some 18 ga black insulated wire that I got from Fry’s which is quite small and stealthy so that’s what I used.
For each corner I used a coax T and a coax type elbow. This makes it easy to connect a small rope for support. So I put a PL-259 connector on each end of the horizontal wire and on one end of the two vertical wires. Note that the first vertical wire from where the coax feed is located is connected to the shield side of the coax while all the others are connected to the center wire. On the bottom end of the vertical wires I put an egg style insulator with a large bolt for a weight.
Eventually I want to hang it off the 2nd story of my house but for now I used a couple of poles to support it. They are both metal poles so I’m sure that de-tuned my Half Square some. It wasn’t very high, the ends of both vertical wires were only about a foot off the ground! I’m sure it would perform better if I could have gotten it higher.
So, how did it work? First off, SWR was about 2.0 on the voice part of 15 meters and dropped to around 1.5 in the CW portion of the band. That tells me that it’s a little long. Lower frequency with lower SWR means it’s too long. Of course, it would have been perfect for CW but I’m not into that.
I got it done about 4:30 in the afternoon and the band was still open to the west and south then so here’s the signals I heard.
Call Half Square Gutter Antenna
JA3YBK S9 S5 (Japan)
PY2ZNZ S9 S4 (Brazil)
CE2xxx S3 S1 (Chili, didn’t get his full call)
K6UH S7 S1 (California)
Now, remember, my ‘Gutter antenna’ is just a remote tuner hooked up to my 210 ft rain gutter on the house. It works quite well on the low bands (80 & 40) but only OK on 20 and above.
Bottom line: It worked very well! 2 to 6 S units improvement! Remember, an S Unit is about 6 DB of improvement so that is considerable! Now, this could also just show that my rain gutter antenna is just pitiful on the higher bands compared to a dipole.
Hmmm, that’s a good idea, I think I’ll build a 15 mtr dipole and put it up in the yard at the same time as the Half Square so I can compare them! I need two more poles to do that. Got one I can borrow? Needs to be about 20 ft long and non-conductive if possible.
Anyway, I hope you enjoyed my experiment and article. Email me if you have any questions or comments.
73, Dave KD5FX
