December 1966 QST
articles are scanned and OCRed from old editions of the ARRL's QST magazine. Here is a list
of the QST articles I have already posted. All copyrights are hereby acknowledged.
with most hobby and how-to magazines, QST has had a long-running
monthly column featuring handy tips from readers and sometimes from
the column editor's (currently Steve Sant Andrea) own experiences.
It has taken various names over the years such as "Gimmicks and
Gadgets" and now "Hints & Kinks." This installment from the
December 1966 QST presents a short introduction to a VHF 'Lazy-H'
antenna for mounting in the attic (outdoor restrictions were common
even half a century ago). It is of simple construction using lamp
cord in the configuration and element lengths given - still useful
V.H.F. Lazy-H Antenna
Gimmicks and Gadgets
An Attic Array for Cliff Dwellers
Getting an indoor antenna to perform satisfactorily is not always
easy. Certain sacrifices will result from any attempt to install
an indoor antenna. Yet, by taking advantage of broadband antennas
and effecting the best possible impedance match to them, worthwhile
results can be secured from an "attic special."
Lazy H described in this article is an old standby which should
bring back a few nostalgic memories to 10- and 20-meter operators
who have dabbled with combinations such as this. The entire system,
including 40 feet of 300-ohm ribbon line, cost the author less than
two dollars. It took about 45 minutes to cut the wire to length,
tack the system to the attic wall, and adjust the matching transformer
for an s.w.r. of 1:1. At optimum efficiency this antenna theoretically
should be capable of a maximum gain (bidirectional) of about 5.9
decibels. The overall efficiency will be governed by the placement
of the array with respect to house wiring, water pipes, gutters
and downspouts. The antenna should be kept as far away from such
things as possible, to lessen the chance of pattern distortion,
detuning effects, and absorption of the signal.
Of any number
of simple indoor antennas tried for operation on 6 and 2 meters,
the Lazy-H has been superior to all others used.
Making The Antenna
A 10-foot length of a.c. zip
cord was used for the W1CER Lazy-H. The cord was split at one end
and the two conductors were pulled apart, making two 10-foot lengths
of insulated wire. Each wire was pruned to a length of 115.5 inches
and pinned to the attic wall in the configuration shown in Fig.
1, so that their center sections B-B, crossed. A piece of cardboard,
3 1/2 inches square, was used as a spacer at the point where the
two are transposed, permitting uniform spacing to be maintained
between the phasing line. The insulation was stripped from the wires
at the points marked X, permitting the matching transformer to be
soldered into place. The matching transformer was fashioned from
a 20-inch length of 450-ohm open-wire line.Tuneup
is used at the author's station for
coupling the v.h.f. equipment to the 300-ohm transmission lines
which feed the antennas. Initial tests were made by terminating
the transmission line with a 300-ohm noninductive resistor and applying
a few watts of transmitter output power to the line through an s.w.r.
bridge. The Transmatch was adjusted for a 1:1 s.w.r. reading and
the dial settings were noted on paper. Next, the terminating resistor
was removed and that end of the feed line was tapped along T1
experimentally, until a 1:1 match was obtained at the same setting
of the Transmatch controls that gave a 1:1 match with the 300-ohm
termination. The dimensions given in Fig. 1 should be well within
the "ball park" and should provide a close match at 145 Mc. The
matching transformer should be adjusted for your favorite portion
of the band. Frequency excursions to other parts of the band will
be possible, but the s.w.r. will rise somewhat as you depart from
the part of the band to which T1
has been tuned. The
Transmatch will permit matching the transmitter to the line and
will disguise the slight mismatch at "off" frequencies, enabling
the transmitter to load up normally. If coax line is preferred,
a balun transformer1
can be attached to T1
in place of the 300-ohm transmission line after the system has been
tuned as just described. This will permit the use of 75-ohm coaxial
line, if desired.Performance
the Lazy-H is a bidirectional array, it should be oriented for maximum
radiation in your favorite direction. In the author's case, north-south
directivity was desired so the array was tacked to the south wall
of the attic. Although maximum radiation is at right angles to the
plane of the antenna, some side response exists, making it possible
to work in all directions but with reduced efficiency off the ends
of the antenna.
1 - Dimensions for the 2-meter Lazy-H antenna. Make certain that
center sections, B, are transposed as shown.
an hour of casual listening with an SR-42 transceiver, several W2
stations in New York and New Jersey were copied Q5 while using the
Lazy-H. Stations as far north as Massachusetts were also received
well above the noise level of the receiver. Many of the stations
heard were more than 100 miles away, offering proof that the antenna
was performing satisfactorily.
An antenna of this type should
deliver comparable performance on 6 meters, provided careful attention
is given to the dimensions and to the matching. Complete data covering
antennas of this variety is given in the ARRL Antenna Book,
Chapter 4. An outdoor version of the Lazy-H could be fashioned by
mounting the elements on 1 X 1-inch lumber support arms. It would
then be possible to rotate the array, and greater efficiency should
be possible since the antenna would then be out in the clear. -
W1CER1 The Radio Amateur's
V.H.F. Manual, pp. 188-189.