Some experiments on use
of "printed" VHF magloop (i.e.,
magloop made on a PCB) were made at the 2- meters band.
Loop has square shape and wide of printed wire in 5 millimeter.
50-Ohm coax was matched with the magloop
by a coupling loop. Figure 1
shows the design.
Design of the Magloop: Coupling loop (item
1) is located in the corner of the magloop
(item 2). Rigid coax (item 3) has 8 centimeters length and fastened
to the PCB by a clamp (item 6). Treads (that hold the coupling
loop) (item 5) go through holes (item 4) in the PCB.
Matching: The magloop is connected directly to a VHF hand- held turned
on to Low Power (100 mW). Firstly the
perimeter of the coupling loop consists of 1/3 from perimeter
of the magloop. Do matching of the magloop
by decreasing of the perimeter of the coupling loop.
Do tuning of the magloop capacitor
every time when you decreased the perimeter of the coupling loop.
Field Strength Meter shows you how coupling loop work. I used
FSM described at Reference 1.
Passband of the Magloop. Passband
of the magloop was near 2.0 -MHz at
the 2- meters. The passband was determined
by FSM by decreasing of the RF level in twice compare to central
Theory and Practice. MMANA (see Reference 2) allows to suggest that the magloop has gain minus 5…- 7 dBi.
Practical test of this magloop have
shown that on the open area the antenna was equal to hand- held
helical antenna in 14 centimeter length. However the magloop
do the same job as a lambda/4 vertical (50 cm at 144 MHz) when
communication was inside and from concrete buildings.
Caution: Sometimes (at some cheap hand- helds) the magloop (working at
transmitting mode) could be seriously worsen
the quality of the signal because of the strong magnetic inducing
to the transmitter.