LF: New loading coil operative, new top hat...]
Sun, 04 Apr 1999 11:50:22 -0400
M. Bruno wrote:
> 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")