10-Foot Circumference 30-meter TX/RX Loop

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Joined: 2010/08/02 - 19:26
10-Foot Circumference 30-meter TX/RX Loop

Greetings All

I fabricated a 30-meter TX/RX loop recently and am TRULY amazed by its performance !
Easy to tune for VSWR ~1:1 using an AA-170 impedance analyzer connected to the small
feed-loop .

I used 10-feet of copper tubing as the loop inductor and a length of RG-8 coax center-
conductor/dielectric (shield-braiding stripped off) inserted into the tubing as the tuning
capacitor. One end of the COAX-center conductor was soldered to the inside end-surface
of the loop-tubing and the free-end inserted into the other end of the loop-tubing.

Tuning (stretching/pulling the loop-ends to vary the tuning capacitance) the main loop to
achieve resonance between loop inductance and tuning capacitor, in addition to adjusting
the loop diameter of the small feed-loop, provides close to 1:1 VSWR at the WSPR
10.140200MHz TX frequency.

I do see some tuning drift during a WSPR transmission at a power level around 25-watts
due, most likely, to dielectric heating of the tuning capacitor. At 5-watts the loop
VSWR remains steady at 1:1 . . . . Geez, what a performer in a CC&R limited QTH !!

See ===> http://brisdance.com/vk4amz/LOOP.html
and ===> http://www.66pacific.com/calculators/small_tx_loop_calc.aspx

73 Dick - w7wkr/7 at CN97uj