[Lf] receiving Loop with Litz wire

[Andre' Kesteloot]

Talbot Andrew wrote:

> This weekend just as an experiment, I rewound a small magnetic loop
> antenna using 2.5mm (approx) diameter cotton covered Litz wire recently
> obtained from the Crawley club sale.  The results were impressive to say
> the least !
>
> Loop 1m square with  22 turns of wire (which was all that I had) - total
> wire length 88m
> DC resistance 0.75 ohms, inductance 1.66mH, interwinding (stray)
> capacitance 260pF
>
>         Frequency       Qu
>
>         140kHz          120
>         78kHz           134
>         12kHz           145
>
> The 12kHz result is particularly impressive as a Q of 145 gives an RF
> resistance of 0.86 ohms - almost, within measurement error, the same as
> the DC resistance.   Furthermore, these Q values were in the shack
> surrounded by metal, mains wiring etc so should be higher still outside
> in the clear.
>
> A radiator efficiency of -60dB at 137kHz suggests it may just be
> suitable for transmitting with low power.  However, even  5W drive power
> would give many kV across the tuning capacitor, not really ideal with
> close spaced cotton covered wire.

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