Here's another posting from the BARK PBBS...Keith, WB2VUO =================================================================
First off, I don't claim this to be an original idea here, in fact, what brought this back up was a roundtable conversation on 2 Meters during my last trip to Allentown, PA, and the station using the "SQUARE"-pole had grabbed the idea from an old antenna book, combined with the now-discontinued Cushcraft `Squalo' antenna. Cushcraft, back in the early to mid-60's sold the `Squalo', which was/is an omni- directional horizontally-polarized antenna. It was best know for being used as a mobile antenna for 6 Meters and up, but Cushcraft actually sold scaled-up versions for Base-station operation all the way down to 40 Meters! I recall ads showing a "Christmas-Tree" of `Squalo' anatennas with the 40 Meter model on the botttom, and the other bands arrayed up the mast. It looked neat, but, electrically, the 40 Meter model should have been on TOP, to get the best electrical performance.
2 Anyway, back to the present...
The "SQUARE"-Pole is a 1/2-wave dipole that has been bent into a square. This is the principle of the `Squalo', and the halo is the same idea, but the dipole is bent into a circle. There is some cancellation of energy on a line through the `gap' opposite the feedpoint, but it is minor in the `real' world performance. The unit under discussion down in Allentown was cut for 40 Meters, and the `gap' was 4 feet long.
The first version fabricated was 66 feet in circumfrence, and the spacer was 1/2-inch PVC pipe. When it was tuned up, it looked good, but when 400 watts was applied, the PVC heated up and CAUGHT FIRE!!! The second unit used ceramic egg insulators, and a length of P-Cord, which is a synthetic rope that is available in sport shops. This provided adequate insulation, and low dielectric losses. The resonance was at 7150 KHz, so the length was slightly longer that a straight dipole. I have worked out a chart, base on the resonance shown on the working model, and based on 470/F (MHz) for the total wire length, and with the 4 foot spacing scaled to the other bands.
The "SQUARE"-Pole is installed as a horizontal loop, with the corners run through egg insulators, and rope run out to the supports. As you can see from the chart above , even the longest side on 80 Meters & up can be ties off to the side of the average house, and the longest side on the 160 Meter version will fit across the "average" lot. The minimum height requirements are the same as you would use for a regular dipole, as high as you can get the antenna, and, if possible, at least 1/4-wave up. The installation should be as close to flat as possible.
Coax connects to points marked `X'
Frequency......Total Length......A.......B......C.......Insulator -------------------------------------------------------------------
1.85 MHz......254.0'...........33.8'...67.5'...25.8'......16'
3.60 MHz......131.0'...........17.4'...34.8'...13.4'......8'
3.85 MHz......122.0'...........16.3'...32.5'...12.3'......8'
7.15 MHz......65.7'............8.7'....17.4'....6.7'......4'
10.12 MHz......46.4'............6.3'....12.6'....4.3'......4'
14.20 MHz......33.2'............4.4'....8.8'.....2.9'......3'
18.14 MHz......26.0'............3.6'....7.3'.....2.1'......3'
21.20 MHz......18.8'............2.6'....5.2'.....1.6'......2'
28.40 MHz......16.6'............2.3'....4.7'.....1.3'......2'
50.30 MHz......112.5"...........15.6"...31.1"....9.6"......12"
[ PLEASE NOTE THE 6 METER DIMENSIONS ARE INCHES, NOT FEET!]
Back when I ran the `Squalo' as a fixed-station antenna, I noticed basically no difference between the dipole I startd out with and the `Squalo'.
There was a very slight `null' in line with the gap, but it didn't really affect the overall operation. The 40 Meter version discussed on the roundtable I was in was getting good reports, but the user put it up due to limited room, and would have run the dipole if he had the length to do so.
I am going to install one here when the time permits, and will write up my findings and post them here. I will probably run the test(s) on 40 Meters, although 10 Meters is also a possibility. More to follow...
So, if you want to get on 160 or 80, or need an "inside" antenna for the other HF bands, the "SQUARE"-Pole might be your answer. In fact, you could fit a 40 Meter version on top of your camper/RV/Mobile home...
What a thought! I bet it would fit on top of a Semi, too!!!
73, Keith, WB2VUO, QRP-L #582
Trustee, KB2YTW/B 10 Mtr Beacon (28.2860 MHz)
"In the Depths of the Great bergen Swamp...FN13ac"
Thanks to Keith WB2VOU for passing on the information.
Frank G3YCC