K9AY Low Band Receiving Loop System
The AYL-4 is the popular K9AY 4 way Loop receiving
antenna, as described in the September 1997 issue of QST, “The
K9AY Terminated Loop-A Compact, Directional Receiving Antenna,”
by Gary Breed, K9AY at
AY Technologies
This system provides a cardioid directional pattern
in four different directions. The AYL-4 consists of two units,
an indoor control box and an outdoor direction-switching relay
box. The control box includes a 15 dB preamplifier with a bandpass
filter covering the 160 and 80 meter bands, with excellent rejection
of Broadcast Band signals and signals above 5 MHz. The AYL-4 is
used with two loops installed using a single support, oriented
at right angles to one another. It is intended to be used with
either the AYL-M mast, hardware and wire package, or with “homebrew”
loops constructed by the user. The wire system at GM7NVA utilises
the circumference of a 100 year old apple tree with the switching
unit fixed to the trunk of at the tree.
Specifications
Antenna type: Terminated loop
Pattern: Cardioid, switched in four directions
Peak front-to-back: Greater than 20 dB, typically greater than
30 dB
Feed point impedance: 50 ohms nominal; low-loss transformer matching
to the antenna
Frequency range: Very low frequencies to 5 MHz, using published
dimensions
Direction change: Feed point/termination switching relays
Direction control: Indoor and outdoor units connected with a 6-conductor
control cable
RF connection (antenna): SO-239 (UHF) connectors at control box
and outdoor relay box.
RF connection (radio): Phono connector output to receiver external
antenna input
Termination Adjustment: Eight resistance values from 340 to 680
ohms, selected by front-panel rotary switch
Power requirements: +12 to 13.8 VDC, 400 mA max., (provided by
customer, to be fused at 0.5 A)
Preamplifier: 15 dB gain, feedback type, using a silicon NPN transistor
Filter passband: ±2 dB from 1.75 to 4.5 MHz
Filter stopband: –55 dB at 7 MHz, –50 dB below 1450
kHz (typical)
The standard AYL-4 K9AY Loop System when supported by a single
mast, requires 15 feet in four directions from the center of the
antenna, plus additional distance depending on the guying method.
The base of the supporting pole and the ground rod are located
at the centre. With the AYL-M kit, 21 feet in each of the four
directions is required. The centre support is 25 feet high, and
must clear any objects above.
The two wire loops (85 feet long) wrap around the apple
tree branches to create the maximum area within the loop. The
four wire ends are connected to the relay switching box. Loop
1 is connected to the two red (A + C) and the second Loop to the
black terminals (D+B). 'A' direction favours Europe, North Africa
and Middle East. 'C' North America with 'B' to Japan and 'D' South
America and East Africa. I use a separate Beverage for Australia
and Central America.
The apple tree that doubles as the 4 way loop support.
The wires run around the circumference of the whole tree.
A simple plastic bag is used for weather protection.
The heavy green wire is the ground connection to a 5 foot copper
rod with four 12' radials on the ground surface.
The commercial package from AYT.
