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I fo und it more convenient t o attach an
50-239 connector so that t he coax cable
could be mo re easily connected. Details are
given for making a bracket to mount the connector.
(Naturally, this idea ca rn e after vaca-
self. Place the fo ur radials into the connectors
and tighten the screws securely, yet not
enough to deform the conduit. Attach the
whip to the center connector, then screw t he
reso nator to the top o f the whip. Foilow the
manufacturer's instructions fo r adjusting the
resonator to the lowest swr. 1 did have trouble
bringing the swr down on the 75 meter resonator,
due to poor ground co nditions. (After
all, five foot long radials at 7S meters is a
joke!) The problem was relieved so mewhat
foilowing a suggestion by WA 2AOD : use
kitchen aluminum foil swiped from the XYL
to increase the ground plane. Four I S' long
strips placed under the radials helped get my
signal out with acceptable performance.
• •
End v i ew of w hip showing t he 3/8-24 bolt which
sc rews into mobil e-an ten na r esonators.
tion!) The center wire from the co nnector
is soldered to t he co nd ui t thro ugh a ho le
made for the purpose. If you do not wish to
use a connector, the coax can be soldered
directly to th e whip ;the shield being soldered
to the stub.
Base
The base is made from a 4" square electrical
junct ion box. Be sure to use one with
12" kn ockouts. Five 'lS:" conduit co nnectors
are screwed into the kn ockout holes, as
shown, wit h their screw heads facing upwards.
Don't overlook this simple point, otherwise,
it will be aw kward to disassemble the antenna
for tak e-down. Here's another bit of
hindsight : the top of the junction box is not
too sturdy, owing to the knockouts stamped
in the metal. Make a plate to fit over the top,
as shown in the illustration. Screw or rivet
this reinforcing plate to the box, then install
the center co nnector. You will find this arran
gement holds up much be tter, especially
if you anticipate small boys will be using your
antenna for a " May pole."
Support-Radials
The four su pports/radials are made from
five foot lengths o f cond uit. F ive feet is a
conve nient length to carry. and two can be
cut from o ne 1O-foot len gth of conduit (standard
length). Don't make them any short er,
or mechanical stability and antenna radiation
will suffer. If you can make t hem longer, so
much the better; especiaily if you intend
doing any work on the 80 and 40 meter
bands.
Setting Up
Using the antenna system is simplicity it-
Some Other Ideas
The success of this arrange ment prompted
me to do some ex perimenting after we
returned home. Using the sa me base. 1 made
an 18' vertical antenna using one 10' section
of co nduit , joined with a regular Vz"-to-'lS:"
coupling. The antenna was base loaded with
a coil. While the junction of the t wo lengths
of conduit was not the strongest, I did manage
to keep the antenna u p all weekend and
worked quite a few stations on 80 and 40
meter CWo (This, by the way, was done after
the junction bo x top was reinforced as described
above.) As a practical limit, it see ms
that 20' is the maximum height fo r co nduit
"verticals" because of the lack of rigidity at
the joints. If you could co me up with a
stronger joint , I imagine these might serve
admirably for field day use, with a minimum
of guy ing.
...WB2WYO
MAY 1969
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