The
motor tuned loop
.
Control
cable and coax ..............................Plastic
case and Knob...
This
antenna is made on 3 meters and 26 centimeters of 9 MM.
soft cooper tube with 50 Pico farads butterfly capacitor.
The excited loop have 1/5 of the main loop as a common
law on the loop construction and it is made with coaxial
cable with the braid soldered to the inner wire.

To
home brew a motor tuned loop, you will need a 12 volts
DC motor coupled to reduction speed gear box.
You will need a non conductive material to couple the
aisle of the capacitor to the aisle of the reduction box.
The motor aisle pass trough a hole on the protection plastic
box and a knob screwed to the aisle indicates the motor
rotation.

Magnetic
loop motor control box
The DC voltage must come from a PWM (pulse width modulation) circuit to power the motor with a train of pulses.
This circuits can be searched by "GOOGLE" under the name of "DC Motor Speed Control" or "Motor Speed Control".
This simple circuit uses one or two 555 integrated circuits and one transistor.
On my control unit I have made some additions on the original schematics.
The most important one is a relay system controlled by the command of two
small pressing buttons for a sensitive forward and reverse motor direction.
..
.
.
The
antenna works continuously from 14 MHz to 30 MHz and with
the plug in capacitors I can work on 30, 40, 60 and 80
meters.
I
can operate this antenna on my backpack having the control
box clipped on my belt by a cell phone clip or attached
to the FT 817 by rubber bands.
..
I
can use this antenna on rainy days from my shack. The
boom wood was water proof treated and I protect the black
plastic case with plastic bags.
For QRP base operation from my shack I develop a window
aluminum knee, that keeps the antenna upright facing the
window (when not in use) or horizontal positioned for
operation position.
..
...........HF
QRP SHACK ..............................CONTROL
BOX-FT817-DR36...
..
...ARTICULATED
WINDOW SUPORT................ LOOP
ANTENNA ATACHED.........
....
..
.......UP
RIGHT .................LOOP
ON STAND BY POSITION ..
PY1
AHD ALEX (Alexandre Grimberg).
e-mail:
py1ahd@ig.com.br