By Gary Breed, K9AY
(Source: QST, September 97, pp. 43-46)
Describes a directional receiving antenna for low band use which
is smaller than an EWE but provides equal performance. It is switchable
through four quadrants.
From the earliest days of radio, low-band operators have valued
directional receiving antennas, such as the Beverage, for their
ability to reduce both QRM and QRN arriving from the back side.
Beverages require lots of real estate, so the EWE array described
by WA2WVL in QST Feb 95 was a great step forward since it could
be erected on a modest size lot. Now, K9AY has gone farther and
describes an antenna that can be erected in almost any back yard
and provides performance equal to that of a EWE.
The terminated loop, simply stated, is a vertical loop
of wire, grounded at the bottom center. The loop is fed at the
bottom, through a 9:1 transformer connected between a ground stake
and one side of the loop. The other end of the loop wire is connected
to the same stake through a load resistor. The optimum value of
the resistor is between about 390-ohms and 560-ohms, depending
somewhat on ground resistance and also which band is in use. At
the author's location, 390-ohms gives optimum front-to-back ratio
on 160-meters, and 560-ohms is optimal for 80-meters. A value
of 470 represents a compromise that is reasonably effective on
The shape of the loop is not critical. The author's loop
is essentially a triangle with a 30-foot (9.1-m.) horizontal base
near the ground and an apex supported atop a 25-foot (7.6-m.)
pole. Two of these loops are erected using the same pole and ground
stake, oriented 90-degrees from each other. A switch box containing
relays is mounted on the ground stake and a four-position selector
switch in the shack allows the operator to switch the feedline
between either side of either antenna, and the load resistor to
the corresponding opposite side, so as to select azimuth quadrants.
The direction of maximum gain is in line with the plane of the
loop and toward the side containing the feedline.
The size of the loop is also not critical. Larger ones
capture greater signal voltage, but also more noise, so the signal-to-noise
ratio is unchanged. If the loop is too small, a low-noise preamplifier
may become necessary. The author's antenna provides ample signal
strength on both the 160- and 80-meter bands without a preamplifier.
The author ends the article with a suggestion that he has
not tried. The terminated loops are sufficiently small that it
would be easy to build a four-square array of them. This would
greatly increase F/B ratio and also narrow the forward lobe substantially.
One would have to remember to switch the direction of each component
whenever that of the whole array is switched.
intention of this digest is to give readers sufficient information
to decide whether to obtain a copy of the full text. To get a
copy of an article in QST, please inquire of other hams in your
own neighborhood. Many have collections of back issues. Anyone
who is unsuccessful in finding a fellow ham with a collection
should try every library in the area, especially those at universities
and technical colleges.
If all else fails, a copy can be obtained from the ARRL Technical
Department, 225 Main St., Newington, CT 06111-1494, USA, for a
fee of $3.00 per copy for ARRL members; $5.00 for non-members.
Remember, it is both cheaper and quicker to obtain one locally.