Re: LF: Re: 1/2 wave 500

[Andy Talbot <andy.g4jnt@googlemail.com>]

That's how submarine communications antennas work on ELF (81Hz or whatever).  A very long wire is grounded at the far end.  the skin depth of poor conductivity ground results in a loop antenna with teh current returning deep in the ground

 

Apparantly, a test was done in this country back in the 1960's, using a section of  power grid line grounded at one end and a surplus power station run up, loading into it - presumably at a frequency shifted away from 50Hz. 

 

Sounds an interesting experiment although don't know what results were ever found.   Think of the health and safety red-tape if anyone suggested something like that, these days.

Andy
www.g4jnt.com

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2010/1/14 James Moritz <james.moritz@btopenworld.com>

Dear Mal, LF Group,

Interestingly, if you do an EZNEC simulation of this antenna, it produces an upwards-directed, horizontally polarised lobe as you would expect. But it also produces vertically polarised radiation upwards and "off the ends" like a loop. My guess is that it is also behaving as a long, thin loop, with the missing vertical legs replaced by the distributed capacitance between the wires and ground plane. It would be an interesting thing to try, but quite hard to evaluate the results, I think!

Cheers, Jim Moritz
73 de M0BMU