Hi all,
I have rebuilt my loading coil/variometer, using a plastic
dustbin as support. It works very well, and the antenna current
even increased a bit, from abt. 5,8 to 6 A. Thanks to all OMs for
their suggestions! I extimate the ERP increase in 0,7 dB.
Details of the coil: I have an antenna capacitance of 370 pF,
requiring about 3,7 mH to be tuned. The coil has 100 turns of
insulated 12 AWG wire (2 mm dia., abt 3 mm with insulation).
The wire is a surplus one, and insulation is hard plastics, probably
siliconic (definitively not PVC).
The winding is conic, diameter abt. 450 mm at the base, 425 mm
at top. The variometer has 10 turns on 300 mm dia, and is
mounted on the high (and hot) side for easy of turning.
According to G4FGQ's SOLENOID.EXE the Q should be over 1100 when
in series resonance. Assuming a 3 Ohm series resistance (3,1 kOhm
reactance) the dissipated power in the inductor should be about 100 W.
After 30 seconds of key down or 6 minutes of CQ the coil warms a little,
so I have to believe that Q is high!
Then I am rebuilding the top hat. Currently I use two 27 m wires,
spaced 1 m. The new one has three 20 m wires, spaced 1 m from each
other. It will be more distant from obstacles (house and end pole).
I hope to be QRV tomorrow.
73 de IK1ODO Marco
Rivalta, ITALY JN35SA (N 45 01' 25.6", E 7 31' 09.4")
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