KL7JR Vertical Pancake Dipole 10-20
I was amazed when I first learned of
the TAK-tenna reduced size dipole on Hamuniverse.com.
I immediately was inspired to homebrew the design but for vertical use.
Sometime about a year a go I contacted Steve, WA2TAK, to see if he
experimented with his design as a vertical dipole. His answer was "no",
but now Im seeing references on the internet where some hams are trying it
vertically with good results.
After a trip to Home Depot, heres my
version of the design by WA2TAK (*which appears similar to K6NOs spiral
tuning coil type antenna. See footnote
I originally was going to use a PVC backbone,
and then I thought about using plastic lattice until I saw the plastic
diffuser sheets used for some fluorescent lights.
I purchased a sheet 18 inches wide by 36 inches long.
I cut out two pieces (one per leg of the dipole using side cutter pliers)
23 inches by 15 inches. It is not recommended for outdoor use as this
material is too fragile..oh did I mention I was going to use this as an
indoor antenna in a limited space situation (landlord says no exterior
antennas), in my four foot high window and go QRP maybe to avoid problems
with my neighbors? What a challenge, eh?
Saving grace, is that my
apartment is on the 14th floor of a high-rise , so the added height above
ground may be that little extra help I need on this
My living room window sill was about 12 inches wide,
so the antenna had to be a rectangular loop of wire to better fit vs. the
round popular style, and the boom is made from 3/4 inch PVC pipe (40
I used #16 stranded insulated wire. Each leg was
about 20 feet long which should yield 10-20m for sure, and just maybe 40
meters if the antenna works at all.
When the dust settled, I had about
$30 invested in this design and it took about 3 hours to build.
The antenna easily loaded 10-20 meters in the
vertical configuration but it didnt do well for me on 10 and 17 meters as
a horizontal dipole. With this in mind, I concentrated on the antenna for
vertical use. Your particular set up may show the opposite results. On a
mid March weekend (2009) under more poor band conditions, I heard two
stations on 20 meters and worked them both. An Oregon ham and I exchanged
5x9 reports, and in California I received a 5x4 report and gave a 5x7. My
power level was 50 watts.
I forgot to try it on 40m but since it
easily loaded on 20, Im thinking 40 is possible as well. Im pleased enough
with this design to further experiment as an indoor vertical using "long
coils" as I did with my 10-40 meter vertical
dipole using 102 inch steel whips. This would no doubt make a good
antenna design should you have the luxury of being able to mount it
outdoors and perhaps tweak it a bit!
Have fun antenna experimenting. 73 de Yukon
Antenna resting high above the Alaska
(That's a 12lb "dirty" snow ball holding it
Same antenna, same snow,
horizontal position....warming from the cold!
*Bill Petlowany K6NOs
"Petlowany Principle" states that "if a length of wire is wound in to a
spiral-shaped coil, it will then, and only then, exhibit RF
characteristics that closely approximate those of a resonant linear wire
of the same length".