THE LIGHT LOOP
My main goal was design a lightweight magnetic loop antenna to be hand held on QRP pedestrian operation.
This small magnetic loop can be temporarily fixed on a balcony with a plastic clamp, or installed on a car
by the magnetic “Coke-Mount” designed to operate static mobile.
On both situations the tuning knob is easily hand reached for antenna adjustments.
One of the challenges was to build this hand held loop with the variable capacitor on the bottom
and the inner loop on the top to optimize the antenna’s gravity point to improve the weight balance.
The antenna weight is less then 690 grams.
The normally used extension shaft coupled to the variable capacitor was changed by a small
plastic knob for tuning the loop at hand holding level.
The antenna loop is made on 271 centimeters of RG213 coaxial cable and the inner loop is made
on 54 centimeters of electric copper wire.
The variable capacitor is a multi gang AM/FM/SW portable radio unit.It has small plate spacing; but despite of this I have no arching problems working on QRP power levels.
The variable capacitor as 5 moving and fixed gang plates and I connected each extreme of the
loop on a group of fixed plates to avoid electrical contact losses. The variable capacitor
fixed gangs was combined in series resulting in 80 Pico farads.
The exclusive magnetic “Coke-Mount” base was designed to operate static mobile
Magnetic “Coke-Mount” parts list:
A) Loudspeaker magnet
B) ¼ Coke plastic bottle
C) ½ Cream cheese plastic cup
D) Thermal fax paper inner tube
PY1 AHD ALEX (Alexandre Grimberg).