Specifications

From March 2008 QST © ARRL
some back and forth and moving the guy
stakes a bit closer to the mast, I got the guys
adjusted and the mast plumb.
I spent the third afternoon attaching the
switch box to the mast, attaching the loop
ends and ground wire to the appropriate
terminals, and running about 200 feet of feed
line and control cable. The control box needs
12 V dc at 400 mA and a coax jumper to the
receive antenna jack on your transceiver. The
control box used a phono jack for the receiver
connection and an SO-239 UHF type coax
jack for the loop feed line.
Putting the Loops to Work
With the wiring finished, there wasn’t
much left to do but turn it on and start lis-
tening. There is only one adjustment — the
eight-position TERMINATION resistance
switch. As explained in the manual and
shown in more detail in the original QST
article, the K9AY loop horizontal radiation
pattern has a very broad front lobe with a
deep null off the back. The null in the verti-
cal pattern is deepest at around 30 to 40°
elevation. The termination resistance estab-
lishes the optimum front-to-back ratio, and
the optimum value varies with local ground
conditions and frequency. After some experi-
mentation over a couple evenings, I couldn’t
improve on the suggested default values for
160 and 80 meters.
On air results were quite interesting.
The first thing I noticed was the absence
of noise and the clarity of desired signals.
Listening on the dipole, with S-7 or stron-
ger noise most of the time, it’s a struggle to
hear weak stations. Not so with the loops.
Although signals are significantly weaker,
with the noise gone they clearly stand out
and are easy copy. My receiver is sensitive
enough that I use the preamplifier/filter in
the loop controller perhaps half the time
on 160 meters and only occasionally on
80 meters. Sometimes the antenna, with the
preamp/filter off, improves listening when
40 and 30 meters are noisy. The loops ex-
hibit noticeable directivity and are effective
in reducing the strength of signals off the
back. The null seems to range from about
two S-units to five or six S-units depending
on propagation and my distance from the
undesired signal.
One interesting question arose a couple
weeks after installation. Winter arrived with
a bang in early December, and four storms
in a row deposited about 24 inches of snow
on the ground, covering the lower loop wires.
A quick consult with ARRL’s antenna expert
Dean Straw, N6BV, reassured me that snow
is actually not very conductive and likely
would not noticeably affect the pattern or
create additional losses. We have even more
snow on the ground as this is written, and the
antenna still works. The outdoor relay box is
Figure 7 — The green fiberglass mast,
black wire and black Dacron guy ropes all
help the assembled AS-AYL-4 MW mast/
wire kit blend into the background. The
gray relay box is mounted several feet off
the ground with the ends of the loop wires
attached to posts on top.
Figure 6 — Response of the preamplifier
and bandpass filter in the AS-AYL-4 loop
controller from 1 to 7 MHz as measured
in the ARRL Lab. The filter is designed
to attenuate unwanted signals in the AM
broadcast band below 1.8 MHz and in the
shortwave broadcast bands above 4 MHz.
with set screws. The bottom of the mast rests
on this ring, which has a series of holes for
attaching a ground wire from the relay box
and for hooking up radial wires.
The mast and loops went together on
the second afternoon. The loops are made
from 88 feet of 13 gauge insulated, stranded
wire. The fiberglass mast is four sections,
each 6 feet long, 1.5 inches OD, with an
1
⁄8 inch wall. You build the antenna from
the top, first stringing the loop wires through
a plastic guy ring that slips over the top sec-
tion. Then you slip in the next mast section
from the bottom.
At this point, the instructions say to get a
friend to hold the mast while you finish as-
sembly. The next steps are attaching
1
⁄8 inch
Dacron rope guy lines to another guy ring,
slipping that over the top of the third mast
section and adding this section to the mast
assembly. At this point you slide insulators
over the loop wires and finish assembling the
guy ropes and fasteners using prescribed di-
mensions. Then you hammer in the supplied
guy anchor stakes at the 90° points (northeast,
northwest, southeast, southwest) and loosely
attach the guys. Finally you lift the assembly,
slide in the last mast section, and set it on the
ground rod mount.
The mast seemed fairly sturdy and my
wife wasn’t all that excited about continu-
ing to work outside on a cloudy 25° day, so
I kept going by myself. While adjusting the
guys, I pulled the top of the mast a little too
far out of vertical and it fell over, cracking
a couple of the mast sections at the joints.
Ouch! I was able to repair and reinforce the
mast joints with some electrical tape and hose
clamps, but do yourself a favor and follow
the instructions. The mast is perfectly capable
of supporting itself and the antenna when
assembled as directed.
Some of the dimensions didn’t come out
exactly as shown in the drawing, but after
still above the snow line, but the white stuff
accumulated on top where the loop wires
attach to exposed stainless steel machine
screws. The box seems to be well sealed
against weather, but I decided to add a plastic
bag to keep the snow away.
After using the K9AY loop system for
a month, it would be difficult to go back to
listening on my dipole. After improving my
transmit antenna next summer I may want to
try a bigger receive antenna, but for now I can
hear more DX than I can work with my low
dipole and 100 W. If you’d like to hear better
on 160 and 80 meters, and especially if space
is limited, the K9AY loop system from Array
Solutions is worth a close look.
Array Solutions recommends their
AS-196 or AS-197 receive front end protec-
tor for those with a close by transmit antenna.
The two are similar, except the 197 model
also includes a lightning arrestor.
Distributor: Array Solutions, 350 Gloria
Rd, Sunnyvale, TX 75182; tel [phone];
www.arraysolutions.com. Price:AS-AYL-4
controller, $325; AS-AYL-4 MW mast/wire
kit, $195 ($110 without the mast); AS-196,
$38; AS-197, $58.
QS0803-PR06
11.5 22.5 33.5 44.5 55.5 66.5 7
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