[Lf] [Fwd: LF: Loops]

[Andre' Kesteloot]

Peter Dodd wrote:

> > If you're building a loop don't forget that a lot off turns side-by-side
> > constitutes electrically another loop at right angles to the main one, much
> > smaller perhaps but quite enough to knock the notch down from a possible 50
> > dB to only 15-20 dB. For this reason flat "pancake" loops are better.
>
> Provided you are not too bothered about the deep nulls loop antennas
> with side-by-side windings are good for DX if they are over a metre
> in diameter. This construction (see the PA0SE design in the RSGB
> Communication Handbook and the G3LNP design in Radcom July 1999)
> allows the individual wires of the windings to be spaced to reduce
> the loop internal capacity and increase the Q.
> In the early days of experimenting with 73kHz, G3XDV and I used
> ferrite loopsticks from transistor radios for with mobile receivers.
> While these antennas, even with an FET amplifier, are no good for DX
> they do have very sharp nulls.
> Ferrite loop antennas can be used for DX. See the 160m design, using
> lots of ferrite, by Richard Q, Marris, G2BZQ, in the ARRL Antenna
> Compendium, Vol 6. Could this be modified for 136kHz?
> Has any one seen, or even posses, one of the large flat slab ferrite
> DF loop antennas used in the RAF (circa 1960)?
> I can confirm that a 1.5m LF loop antenna made from computer multi
> colour ribbon performed badly.
>
> --
> Regards, Peter, G3LDO
>
> <g3ldo at zetnet.co.uk>