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Tune Around! Topics For
Technicians! |
Having seen the performance of the 15
meter hentenna I built,
 Look closely for the wires going to the top on each side. This is how I did it and you can
too.
Using the formula from the "Hentenna Revisited Project" on Hamuniverse.com,
(refer to it if needed). I came up with the following: I used 14.300Mhz as the design frequency. 15744/14.300 Mhz which gave me 1100.9 inches or 91.74 feet
total wire for the rectangle.
5904/14.300 Mhz = 412.86 inches or 34.40 feet for the
sides.
1968/14.300 Mhz = 137.62 inches or 11.46 feet for the top
and bottom.
1180/14.300 Mhz = 82.51 inches or 6.87 feet for the
feedpoint.
Note: As the feedpont varies with the material used (#14
AWG stranded, insulated wire) you may need to move the feedpoint up or
down to resonance. The feedpoint will be between 1/6 and 1/10 wavelength.
With this wire the feedpoint has been closer to the 1/6th WL so I
used this formula: 1005/14.3/ 1/6 which gave me 11.8 feet for the feed
point on each side.
I cut 92 feet of wire to allow for the solder
joint, joined the pvc so that I had 2 ea 11 1/2 ft. pieces for the
top and bottom, fed the wire through the pvc and soldered it. This
automatically gave me 34 1/2 foot sides when hanging. Neat, huh?
I also added a "dirty balun" consisting of 8 turns of coax wound on a 2 liter bottle seen in the photo below in the red circle.
I pulled the top pvc up through the bough of a tree and stripped 2 feet of insulation from the wire between 10 and 12 feet on each side, attached the coax to the feedpoint wires and moved it to where the swr was below 1.8:1. The Hentenna is very broadbanded so I knew at 1.4:1 say, I would not have any problem with the phone portion of the band. I then hoisted it up as high as I could (need to get
it in a taller tree but have to wait till the leaves fall or put up the
100 ft. tower). Needless to say the results were amazing.
On the air performance! I worked more stations from Brazil to So Cal and of course more TX, AZ, and most said they thought I was pushing my "amp" pretty hard (I was running 50 watts and had the mic gain at 50%!). I turned the mic back to 20% and it is a hand mic! That made them happy, HI HI! I worked every station I tried on no more than the 2nd call. There was the Texas county contest going on and as AD5WB said from Galveston "You got a BIG signal in here." I am guessing that the 1 1/3 wavelength helps as it is using a full wave on frequency with 1/3 wave to match. The Hentenna has outperformed
any dipole or loop I have ever built.
It has a smaller footprint than either and is easy to construct. The tree did not present any problem even as close as it is. I am working on other projects with the Hentenna and am excited about it. I will provide updates as I finish and prove the antennas I am building. This is why I love doing these projects myself. There are so many "claims" for antennas that I usually disregard them. I have to have the antenna "prove itself" to me. This design certainly did! 73 de N5NNS
George
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