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LF: Re: Near field of 9kHz antenna IV

To: [email protected]
Subject: LF: Re: Near field of 9kHz antenna IV
From: "Andrew Talbot" <[email protected]>
Date: 16 Jul 2001 09:43:42 +0100
Reply-to: [email protected]
Sender: <[email protected]>
For our garden sized antennas I think that resonating a wire is completely impractical at these frequencies.  What I intend looking at, (if a 9kHz NoV ever happens :-(   is something like a ground loop.  I'm basing the idea on the US Submarine comms experience at ELF / ULF. (Have a look on the web at Project Sanguine I think its called)   If a really long wire is laid out at low elevation - just lying on the ground even - then fed against a real earth connection then a ground loop will be set up.  There will probably not even be a need to ground the far end.   With a skin depth, particularly in low conductivity ground, measured in 10s or 100s of metres then quite a large loop will result.
 
I know ground loops were tried on 73kHz, with only moderate sucess, but the much lower frequency ought to improve the efficacy of the system.   Even in my urban plot, it will be possible to lay out several hundred metres of wire by just trailing it over the garden wall and along a grass verge by the road.   I'll be limited in wire length only by roundabouts where the verge stops.
 
Andy  G4JNT
 
The corrected figures are even more dramatic than for the loop.
 
To feed 1kW into the 180m high 15mm copper pipe the current must be 154A and the voltage on the antenne becomes 2.5MV! Perhaps the pipe would survive the current but the voltage makes the system completely unrealistic (corona).
 
And what would the required 286mH loading coil for that voltage and current look like ...


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