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Recently I have been experimenting with small form Flag, Kaz, SuperLoop, and
DKAZ antennas.
My first throw at moveable support poles has been with sections of PVC pipe
mounted in heavy duty patio umbrella bases.
Typically I will use a 6 to 7 ft. (~2m) piece that fits snugly in the umbrella
stand and then a skinnier piece of similar height that is inserted a short way
(less than a foot) into the bottom PVC section. 1/4-20 hardware with a wingnut
connects the lower and upper PVC sections a few inches below the upper edge of
the lower PVC piece.
This allows a 10 ft. / 3m side antenna height above the bottom wire height of 2
ft. / 0.6m (= top of antenna 12 ft. above ground). With the Flag design, the
center insulator on each side (where a transformer or termination resistor
would be installed) is about 7 ft. above ground.
By moving the umbrella stand pole assemblies about on the lawn, different null
directions can be selected. Distance between the poles is typically set about
20 ft. / 6m for Flag and SuperLoop antenna types. Nylon mason's twine attached
to a cinder block or brick is attached to each pole just below the top to act
as a guy rope opposing the pole bending caused by wire tension. That keeps
each pole roughly vertical.
With the rather small loop dimensions of 10x20 ft. / 3x6m, a moderate amount of
low-noise amplification is recommended at the shack end of the feedline. The
DX Engineering RPA-1 or a W7IUV amp would be a good choice.
The present design is OK for use in my own yard but a bit clunky for road trips
to beach DXpedition sites since the hardware needs to be removed from the lower
+ upper PVC sections junction to allow loading into the car. Then the antenna
has to be reassembled on site and knocked down again when departing. 7 ft. is
about the greatest length I can accommodate with the trunk closed on my Subaru
Forester.
Ideally I would like to use poles that can be scoped down to about 6-7 ft. and
extended well above 14 ft. I have read a number of articles recommending
telescoping fiberglass poles of various types. I looked around Home Depot and
found a few candidates but was unsure if they were completely non-metallic, an
important consideration for various types of terminated loops. Also it seemed
that anything that would extend much more than 12 ft. would not scope down to
much less than 8 ft.: likely too long to fit in the car.
Many of you are using various painter's poles, lineman's poles, fishing rods,
etc. to deploy loops (both terminated cardioid and conventional figure-of-eight
types) at field sites.
Given the idea of non-metallic material and a maximum scoped-down length of 7
ft., what are everyone's ideas?
These things don't have to tolerate years of bad weather but they should not
self-destruct during a few hours in high winds typical of seashore or
mountaintop sites.
The suggestion box is open. Fire away!
Mark Connelly, WA1ION
South Yarmouth, MA
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