Glendora Emergency Response Communications

Try this easy to build ''Hentenna''

Feb 14, 2006

All Copper Pipe Hentenna Version for 2 Meters

Edited from an article by Terry, WA0ITP

The Hentenna is a loop style antenna developed by Mr. Tadashi Okubo JH1FCZ, Mr. Someya, JE1DEU and others in Japan in the 70's. It was first described in the US in a Feb 1982 QST article by Koji Sugihara, JJ1UMS and Shirow Kinashita, JF6DEA/KE1EO wrote about it in the ARRL Antenna Compendium Vol 5. The gain is approx. equal to a 3 element tribander, JH1FCZ reported 5.1 dBd in 1972, yet it is small compared to a beam. (This info was gleaned from the article on page 11, ch 12 of Simple and Fun Antennas by K8CH and N6BV)

2M HENTENNA BUILDING AND INSTALLATION
Detailed instructions on development, construction, and installation of this great little antenna!


BUILDING IT

I recommend building the 1/2 " copper pipe Hentenna to these dimensions.
overall length = 40 inches
overall width = 12 3/4 inches
feed point = 7 3/16 to center line of T connector

You'll need one 10' piece of pipe, four right angle elbows, two tee's, and two end caps from the hardware store, total cost about $12. With the dimensions below you can just jam it all together heat and solder and it will work just fine. Or you can be a little fussier and adjust the dimensions perfectly before soldering.

Cut the pipe as follows: (use a tubing type cutter, a hack saw?’s too awkward,unless you're really good)
2 pieces 31 13/16" for the long side pieces above the Tee's
2 pieces 6 1/16" for the short side pieces below the Tee's
2 pieces 11 1/2" for the two end pieces
2 pieces 5" for the feed points.

Use tin/lead rosin core solder, and shine up the ends of the pipe before soldering. I just laid it out on the garage floor to keep it flat and applied the heat. Be sure to wear safety goggles since concrete may "pop off" little pieces when overheated. The caps go on the end of the feed tubes and the distance between them will be around 3/4". Solder the coax braid to one cap and the inner conductor to the other.

Notes from KG6TRD:
Dimensions are very critical because there is no adjustment possible after you have soldered the antenna! It is very difficult to solder coax directly to copper pipe caps. However, if you first solder copper lugs to both of the conductors it will be lot easier to solder to the caps.

INSTALLING IT

Here are several things to remember when installing this antenna.

1. Use a non-conductor for the mast, I used 1.25" schedule 40 PVC pipe.

2. For the vertically polarized version, tape or cable tie the coax to the middle of the end piece nearest the feed point, NOT the mast. Let it hang over the end some then attach it to the mast below the antenna, or side mount the antenna.

3. Use non-conducting hardware to attach it to the mast. Steel or brass bolts have a really detrimental effect on the match. I?’ve used nylon bolts, tape, cable ties, and wood dowels.

4. For a vertically polarized signal for repeaters the 40" dimension must be horizontal to the Earth. The signal is perpendicular to the axis of the feedline. See the pictures below.

5. For a horizontally polarized signal for ssb, the 40" dimension must be vertical to the Earth. See the pictures below.

The swr will be close to 1.0 at 146, and about 1.3 at both 144 and 148. The 2:1 bandwidth is amazing, about 10 MHz.

Notes from KF6DSA:
The mounting of your hentenna is not at all critical as long as you use non-conducting hardware. We even had great results hanging the antenna in the garage less than ten feet off the floor and disregarding orientation! In no case did we get an SWR greater than 1.5 to 1. And we easily brought up all the repeaters we had programmed into our HTX-252 emergency kit radio on less than 25 watts.

ON THE AIR TESTING RESULTS

On the air testing has been gratifying. WA?˜MWW and I conducted a performance test between our qth's, we're 12 miles apart, and he's in what I like to call the great Batavia RFDZ (rf dead zone).

We used 146.52 simplex and adjusting my power levels and his antenna orientations to get a noisy signal from me. The Hentenna proved superior to a 5/8 wave ground plane at the same height, 15' up. This was a "switch the coax" comparison so as to minimize propagation differences between tests. We evaluated both vertical and horizontal polarization and the Hentenna signal was better in all cases, sometimes by as much as two S units.

I also can easily bring up 2 repeaters, one 30 and the other 20 miles distant off the sides of the antenna, using only 5 watts. So the pattern isn?’t too sharp for general use.
Ron, WA0MWW and I have also used a repeater that is 45 miles away with 50 watts. A litle noisy but very Q5 copy.

I hope you have very good luck and get a lot of use from this nice antenna. It deserves much more attention than it has gotten here in the US. Please drop me a note and let me know how it works for you. You shouldn?’t have any difficulty, but if you have any questions please let me know. We should be able to cure any problems you may have.

73, Terry, WA?˜ITP

Email Me: Send message to wa0itp at rew2000 dot com