[Fwd: LF: Helical vs Straight vertical]
Thu, 23 Apr 1998 17:46:22 -0400
> >From Toni, HB9ASB, JN36pt
> Now I have built a second LF-antenna in addition to my helical
> Same Top Load (55m long wire), same earth network, same height (15m),
> almost same place (8m away), but with a straight wire instead of the
> helical. Loading coil is about 3mH on a huge PE barrel with 6mm2 (!)
> isolated litz wire.
> These are the first results:
> - helical is a abt. 50% broader
> - helical gives in general a 2-3dB advantage in reception (same noise
> - helical gives a 2-3dB advantage on transmission (with HB9DFQ in
> - difference is the same for day and night
> My helical antenna is far from ideal. Up to 7m it has a diameter of
> 11cm, then I used a Kevlar fishing pole. resonance is at 170kHz and I
> tune it to 136khz with an additional loading coil at the base, which I
> use also to match the coax (tap).
> For the windings I used litz wire, 6mm2 on the lower part (PVC
> irrigation pipe) and 0.5mm2 on the 9m fishing pole.
> The "earth" consists of almost everything I could "connect" on my 30x40m
> lot, including the water supply and the metal fence, and of several 100m
> of burried wire.
> I did not expect an advantage for the helical and I'm quite surprised.
> If I find a way, I will try to increase the diameter of the helical,
> especially for the upper part.
> 73 de Toni