2 Meter
Hentenna by WA0ITP Follow
the trials and tribulations of Terry as he attempts a 2 meter
version of the Hentenna. (The following has been edited from emails from Terry in the
order of his progress)
"I thought I'd drop a note about my experiences
with the Hentenna. I just built a 2 Meter version of it out of
1/2" copper pipe. It was 39" x 13", a nice workable size for a
gain antenna. I have a friend whose trying to receive two
repeaters 180 degrees apart,, each about 15 miles away, and I put it
together to try at his qth.
Try as I might, I couldn't get
the swr below 2:1, as read with an MFJ antenna analyzer. The
impedance in the 2 Meter band never got below 100
ohms.
Subtracting and adding (More
experimentation)
I fed it with a 104" piece of rg-58, adjusted the
matching point up and down 8" to about 14" from the
bottom. Reading that the impedance becomes lower with a
narrower "aspect ratio", I subtracted and added a couple of inches
to both the length and width, one at a time (copper pipe is easy to
work with isn't it?). I also added another piece of coax in
the line just in case. No improvement, I could only make it
worse. The best match was 2:1, So I've left it
there. I think I should have been able to achieve a better
match. Do you think the copper pipe diameter may be at
fault? I'm gonna hoist it into position tommorrw and
see if it's any better at 20' off the
ground.
Success!!!!!!......at last! Learn from my
mistakes! Don't
measure Swr on a picknic
table! Still using 1/2" copper pipe. I decreased the
overall width slightly, saw a favorable result, reduced it a little
more and achieved 1.4 swr at 147 Mhz, so I quit there. I
wound up with 39.25" long, 12.25" wide, and the #12 bare wire
(on a board) feed point is at 8.75", no
balun. Dean Straw (Simple & Fun Antennas)
modeled it to help out and found nearly identical dimensions using
the 1/2" copper pipe in the model.
I'm happy with 1.4:1, the
feed point resistance is 68 ohms and it's pretty broad: 1.4:1
from 146.3 to 148.2, and the 2:1 bandwidth is 144.6 - 150.6!
Don't try to measure SWR on a picnic table!
What would Hams do without duct
tape? A little time passes and we
continue......
I just returned from the final qth. We
installed it temporarily until we can purchase better quality
coax. The antenna wound up being 15' at the base, on a pvc pipe
temporarily duct taped to a 10' 4x4 doing double duty as dipole
anchors. The swr at 147Mhz dropped to 1.2 to 1 at that
height. and the bandwidth is
astounding! I'll make some more
measurments when we get it permantly installed.and send you some
more info, and probably write a club newsletter article
detailing the thing. Dean Straw, N6BV sent some ideas for copper
pipe construction in an email, however I had already experimentally
found dimensions that were nearly identical and had built the thing
out of pipe. This has been a lot of fun, I agree Ham radio needs
some easy to build, easy to install, cheap, and good performing 2
Meter antennas. This seems to be one of
them.
I'll keep ya posted." Terry,
WAĜITP
NOW LET'S BUILD
ONE Building the Hentenna I used 1/2 inch copper
water pipe as the loop element. Each elbow adds about 3/4 inch
to the overall lengths so plan accordingly. I cut the long
sides to 37 3/4 inches, and the short sides to 10 3/4 inches.
Assemble the loop using 4 elbows and solder. I just laid it
out on the garage floor to keep it flat.
Use SAFETY GOGGLES
or glasses since a concrete floor may pop off small pieces of
concrete when heated by the torch. I used acid flux and non
lead solder from the hardware store but rosin flux should be used
for longevity.
The feed points were made by glueing a piece
of #12 wire from a piece of Romex house wiring to a piece of
1/4 inch plywood. It was moved up and down the loop until a
match was found at 147 MHz., then soldered. Plastic clamps
(wire ties) were used to hold the wire to the loop while checking
swr. Use them in final installation to tie coax to the loop and the
support pipe. It is performing well at the final qth and WA0MWW
is pleased to be able to use two or 3 repeaters that were unuseable
on a 5/8 wave vertical. See pictures
below!
Drawing not to
scale!
Isn't it a beautiful piece of
art! Photography by WA0ITP Go direct to his page for more details on
the Hentenna. Learn more about building, testing and putting it
on the air! Click
here
I hope this helps you build this great little antenna.
WA0ITP.....TERRY
Editors note: From the first email to the
working model of this project, Terry only took a couple of days to
get the 2 Meter version up and running. After a little fine
tuning....now a great project! If you use wood as the support for
the feed wires, seal it well with weather proof sealer or use
plexiglass or some other suitable non-conductor. Seal all coax end
connections from the weather.. Many thanks go out to Terry for
sharing his project with all of us! Great work Terry! Keep EXPERIMENTING and have
FUN!........N4UJW
POWERED BY HAM RADIO!
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