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Easy Tuning o the
David S. Traer, W4AZ K
625 8 th S treet , South
Nap les, Florida 33940
Multi -Element Quad Antenna
Perhaps the most perplexing and o ne of
the most controversial problems facing the
builder of the multi-element quad is element
length or tuning. There are many various articles
on quads each having an individual formula
for element lengths or method of tuning
and matching transmission line to driven element.
Basically, there appears to be two
methods of approach. Compromise luning
for broad banding or " on the button" tuning
for maximum efficiency over a smaller bandwidth.
Since t 95 8, when I first erected a four
element quad, many, many man-hours have
been spent making measurements with receivers
several miles away, field strengt h meters,
vswr meters, impedance bridges, and grid dip
meters. At that time, there were no fiberglass
poles, mounting hardware. or any other
information available on multi-elementquads.
It became necessary to find a more or less
foolproof method of tuning and matching
for maximum energy transfer, with a minimum
of effort and with equipment available
to the average ham. With these points in
mind, I set out to find that method.
Several methods were tried over a period
of time. In each case. the vswr over the entire
band looked good from the transmitter
end-with one exception - t he driven element
was always reactive. It should be well known
that the reactive component of any antenna,
whether inductive or capacitive, does. not
radiate, in addition, the standing waves along
the transmission line are not at the same point
as they would be with a pure resistive load
mismatched to the transmission line in the
same degree alt hough reactance is also measured
in ohms. The proximity to surrounding
objects does not affect the closed loop of the
quad as much as it would a yagi type ant enna.
Work may be done on the quad much closer
to ground level (15-20 feet) if allowance is
made for a frequency rise of ap proximately
25 to 50 kHz at 14 MHz when the antenna is
put back to forty feet or higher. Therefore,
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the quad should be tuned to a lower frequency
to eventually come out at the design frequency
unless all tuning is done at the final
antenna height.
One factor that may be difficult for some,
is that all elements must be made accessible.
If not accessible from your tower or pole, a
temporary 2x4 may be set in the ground high
enough to put the boom of the quad at least
fifteen feet above ground level. An allowance
of 50 kHz should be mad e at this height.
Should the diamond configuration be used,
a slightly higher temporary pole would be
necessary. From my tests there has been no
noticeable difference between the diamond or
the square configuration. Some may argue
that the two high current points in the diamond
configuration, being farther apart, would
tend to increase the gain. Theoretically, this
may be true, but no measurable difference
has been noted here.
Let's take an example of a twenty meter
four element quad in the square configuration
to be tuned to a design frequency of
14250 kHz. Tuning to be done at a minimum
height above ground. First, one must buy,
beg, borrow, or build the following equipment
: grid dip meter, vswr meter, antenna
scope or impedance bridge, and one friend a
mile or more away. The stat ion receiver. of
course. is also a must. You may use any of
the convenient formulas as a beginning because
in this case we are not interested in the
length of wire as measured in feet and inches,
but the results as measured by our eq uipment.
It is always better to have more wire
than needed as it is quite easy to cut off an y
excess. Some use number 10, 12 or 14 solid
copper wire, some aluminum clothes line
wire, or seven st rands of number 20 or 22
plain old antenna wire: which is available at
most all wholesale houses. There are now
many construction articles on multi-element
quads so we will not delve any furt her into
that region.
String the wire and place all elements on
73 MAGAZINE