[Lowfer] Experimental antenna?

Wed, 26 Feb 2003 11:01:31 -0000

For cave rescue (certainly in the UK) ERP usually does not come into it
because we are, more or less, within the near field at the frequencies and
for the depths concerned. We are therefore dealing with an induction system.

Best slant range that I know of at 87 kHz is about 1 1/2 km in French
limestone with Nicola 2 sets. Best one-way is about 2 1/2 km.

Regards,
John Rabson
Editor
Cave Radio and Electronics Journal

----- Original Message -----
From: "Stewart Nelson" <[email protected]>
To: <[email protected]>
Sent: Wednesday, February 26, 2003 6:22 AM
Subject: Re: [Lowfer] Experimental antenna?

> Hi Pat,
>
> This is sometimes called an "earth loop antenna".  In addition to
> the VLF military and amateur applications mentioned, it has been
> used at LF for cave rescue systems.
> See http://www.sat.dundee.ac.uk/~arb/heyphone/ .
> That system runs at 87 kHz.
>
> In the US, the FCC part 15 rules would limit the spacing between
> the pipes to about 50 feet.  There is also less earth penetration
> in the lowfer band, so you would end up with a radiation resistance
> no more than that of an Ashlock loop, probably much less.  However,
> the loss resistance would be at least an order of magnitude higher.
> IMO, a few hundred microwatts ERP is all you could expect.
>
> I don't know what rules apply in Canada, but if a much larger spacing
> would be permitted, you might get decent efficiency.  If a loop or
> a vertical is limited to a very low height, or if the antenna must not
> be visible, it is possible that the earth loop would be the best choice.
>
> 73,
>
> Stewart
>
>
> ----- Original Message -----
> From: "Patrick MacKinnon" <[email protected]>
> To: <[email protected]>
> Sent: Monday, February 24, 2003 7:21 PM
> Subject: [Lowfer] Experimental antenna?
>
>
> > I've been a ham for 15 years, but very new to this list, and will
probably
> > brew up a lowfer transmitting rig/antenna this summer. Forgive this
newbie
> > question, but:
> >
> > Has anyone tried water drilling two parallel copper pipes into the earth
and
> > using this as a transmitting antenna? It just seems to me that would be
a
> > very effective way of inducing LF currents into the ground. (A fellow
ham
> > told me he recently attended a club presentation on VLF and he stated
the
> > earth itself carries the signal. Is this true or did he mis-hear
something?)
> > [or am I so far off base here I'm in for the flaming of a lifetime?
> > remember: please be kind, I'm new to this! :)  ]
> >
> > Thanks!
> > Pat, VE3PMK
> > London, ON, Canada
> >
> >
> >
> > ###########
> > PLEASE NOTE:
> > My anti-Spam policy prevents my attaching an email address in the usual
> > fashion. Please send any replies (if required) to the following address:
> >
> > pat[two zero zero two] at foxhollow ca
> >
> > Convert the bracketed text to the obvious number and the usual "@" and
"dot"
> > is required. This will route email through a very aggressive filtering
> > processing. Sorry for the complexity, but there it is.
> >
> > -- Pat MacKinnon
> >
> >
> >
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