Re: LF: Re: Induction DX?

[M0FMT <m0fmt@yahoo.co.uk>]

Hi Jacek and group

 

That is a very good site and the sound clips help identify stations like the Alpha nav aids.

That is a really dedicated guy, I liked the auto signals I never thought they would radiate so well. I have had a similar experience to his with very low power at a range of about 1/2 to 1 km range at 7.8kc/s but at 1.8kc/s it shows there is promise on these VLF frequences.

 

Thanks for the URL Jacek. That site should be an inspiration to all of us experimental ops!

73 es GL petefmt

--- On Sat, 13/3/10, Jacek Lipkowski <sq5bpf@lipkowski.org> wrote:

From: Jacek Lipkowski <sq5bpf@lipkowski.org>
Subject: Re: LF: Re: Induction DX?
To: rsgb_lf_group@blacksheep.org
Date: Saturday, 13 March, 2010, 9:14

On Thu, 11 Mar 2010, James Moritz wrote:

> It is interesting to try to work out what might be possible by induction...
[...]

have a look at http://www.home.pon.net/785/equipment/transmitting/VLF_transmit_2.htm

this experiment used two triangular loops of 15m high and 90m circumfrence in a natural area (without conductors etc).

the author was able to copy a 0.5W cw signal at the distance of 3.3km!

this is much more, than what is expected from free-space calculations mentioned in this thread. this is probably the effect of the ground (currents induced in the ground excite some much bigger ground loops that make up a "secondary" antenna of bigger size).

another explamantion would be that the field induced at the transmitter site got into the 2m receiver that the author was using, but i hope that is not the case :)

VY 73

Jacek / SQ5BPF