rf - Free and Open Source Software

present one, a boornless quad, was designed
by W4TZ, across town, who had two composite
alu minum spiders electrically welded,
one of which was asse mbled and erected on
the tower by me (age 76) without any help
and without use of a safety belt. The
decision not to use the safety belt loaned by
W4TZ may sound a bit queer. Some 65 or
70 years ago a group at a Wisconsin family
reunion witnessed a dog attempting to scale
a picket gate, as he had done many times
before. He caught the ring of his collar on a
picket and hung there helplessly. Ha nging by
a safety belt, should my foot slip, might
temporarily knock the breath out of an old
man! However, I strongly recommend the
use of safety belt, especially to you younger
fellows with still many years ahead of you.
The accompanying photo shows the composite
spider to have an aluminum plate at
the center with eight short aluminum radials
electrically welded thereto at an angle so
that the spacing between the 2D-meter
driven clement and its reflector is 6 feet 10
inches, wit h a corresponding lesser spaci ng
for the 15- and 10-m eter elements. This
spacing, with the reflector properly tuned at
a sufficient height above ground, resulted in
a unity SWR when fed with RG/8-U or
RG/ 58-U. The Quad handbook says that if
the quad is below a certain height t he
impedance drops to one-half.
Square quads are normally fed at the
center of the lower horizo ntal wire of the
driven element. Since dipoles fed at the
center are said to be a reasonably good
match fo r 72-ohm feeders, and an inverted
..v.. having a 90-degree angle is said to be a
good match for 52-ohm RG/8-U, I chose to
feed my square, boomless quad at o ne lower
corner for the foll owing addit io nal reasons:
I) the feeder may be fastened to the radial,
thereby lessening sway in wind; 2) no need
to pu ll the center of the driven element
upward, out of shape and out 'of true with
the reflector; and 3) it see med to be mo re
convenient to attach the SWR bridge at this
point during tuning procedure. Believe it or
not, it worked!
Fig. 1 shows construction of tuning coil
at the corresponding (b ut opposite) corner
of the reflector. No te the absence of long
tuning "stubs" in the photo, which not only
distort the plane at the current node, but
also tend to affect the adjacent bands. The
tuning co il was formed by winding antenna
wire on a 7/8-inch dowel and, when released,
forms approximately a one-inch diameter
MAY 1969
------\It-f!==~t----
Fig. 1 . Tuning C oil. W hen SWA brid ge eo ­
p roach es u n it, the c l ip A is removed and
t h e sh o r t lead soldered t o t h e t UI n. A c hange
in capacity and configuration of coil might
affect SWA if the sh o r t ed portion of coil
were t o be removed , more so, o n 1 0 met ers
than o n 2 0 and 1 5. L es s turns a re need ed on
1 5 an d 10 meters.
coil. This coil was then spread slightl y and
fas tened to the ends of a somewhat shorter.
thin insulator so that the outer edges of the
turns are spread sufficiently to permit
clipping a short piece of wire to a single turn
wit hout shorting an adj acent turn. Although
less turns are needed for 20 meters. I
started with a 26-turn coil beca use of
the length of the insulator on hand and
made the initial tap at the center turn.
t hereby shorting out one half of the coil.
Tuning was accomplished with a low
power SWR bridge at the feed point where it
could be clearly read at that short distance,
and at a time when the band appeared to be
dead or "out" so as to reduce chances of
interference. Remember, I had no assistance
and had to ascend and descend th e lad der
and tower (more than once! ) to accomplish
the tuning. A short piece of vinyl from the
coax had previously been sli pped over the
clip to prevent rj burn when cha nging taps
o n coil. The coil being at the rad ial. it was
easy to steady it during the tuning process
by grasping the radial with the other hand. It
was only necessary to go a turn or two eit her
side of the original tap to arrive at t he
desired swr. The clip was then removed and
the wire soldered in place. a 50-foot ext ension
cord having furnished th e required
power fo r soldering gun. After re moving the
bridge and replaci ng it near the rig. it was
only necessary to make a two-foot cha nge in
the feeder length to secu re a like SWR
reading of I to I at that location.
J used a 3 -c~ nl, home-made balun. tollowing
the general instructions for a I to J
balun in August 1964 QST. The core is
about 2 inches of ferrite obtained from a
discarded Be loopsti ck, and wound with the
necessary turns of No. 16 copper enamelled
wire. It is not sealed. but merely taped.
Weather? Reports from contacts do not
rn a teri ally differ, whether during dry
weather or rain.
W4TZ uses a common feed er fo r the
three bands. and a quarter-wave sleeve balun
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