Re: Galvanised wire properties


Chris Moulding
 

Hi Paul,

I know from discussions between us that you are trying to emulate the galvanised wire loop that Mike Ladd uses with a Loop Antenna Amplifier + to great effect for his SDRPlay videos and samples.

It sounds from your description that it's working well for you.

Usually I would recommend a loop of 1m or 3ft diameter so that it covers the full HF spectrum up to 30 MHz. If your interests don't cover the higher HF bands then you can use a larger loop. Your triangular loop has sides of 1.25m and Mike's has 1.5 m sides.

The use of galvanised wire is interesting. Usually steel wire is a poor choice for antenna or loop wire due to the magnetic properties concentrating the skin effect into a very thin layer on the surface.

With galvanised wire the RF current will be concentrated into the zinc coating. The resistivity of zinc is 3.2 times that of copper so the losses will be higher.

Another point that may be significant with some receivers is that a 1m diameter loop is resonant around 100 MHz so VHF FM broadcast signals may be very strong and overload the receiver.

A triangular loop with 1.5 m sides will be resonant around 60 MHz reducing the level of VHF FM broadcast signals.

It's interesting to consider why it should work so well, if I can get some galvanised wire locally I'll try one myself.

Regards,

Chris

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