Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

Re: LF: Soil Conductivity Measurement

To: [email protected]
Subject: Re: LF: Soil Conductivity Measurement
From: brian hodgson <[email protected]>
Date: Wed, 3 Aug 2005 19:52:04 +0100 (BST)
Delivery-date: Wed, 03 Aug 2005 19:53:25 +0100
Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.co.uk; h=Message-ID:Received:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=oPiOpIIUNp4Eyezpwm2X0DeXlrCM3rNfMy+s9sSWY1or//Va42jLq0C4H/x4y1iPZWyhTSegJIkKVzmtweJjBeLWM4006bevHJgbiAfO+W9MFMDRlmSjKQ8RyPKphha/jjdMjlZ1gevlEZ8idgExE39meRLY2Or2YhGcnkRHGdY= ;
Envelope-to: [email protected]
In-reply-to: <42F086A9.25339.6CCEF9@localhost>
Reply-to: [email protected]
Sender: [email protected]
Mike Dennison <[email protected]> wrote:

>Although it is interesting to know the ground conductivity, the main
>losses in a small LF antenna are environmental. This includes losses
>in trees, buildings etc. These are sometimes all lumped together and
>misleadingly described as 'ground losses'.
 
Hi All,
 
I've been making some changes/measurements on my rectangular loop
which seem to confirm Mike's findings. The loop is 3.5m high by 8m wide.
It has a DC resistance of 0.5 ohms and an RF resistance (at 136 kHz
resonance) of 0.9 ohms (skin effect?). I recently put two 550 microHenry coils in the
horizontal parts of the loop - each coil has a DC resistance of 1.5 ohms and
a Q at 136 kHz of about 120 ie an equivalent series resistance of about 4 ohms.
 
I was hoping that the total equivalent series resistance would be about 10 ohms
(ie one loop plus two coils) but it measures 40 ohms !!
 
The loop is hung from the branches of trees and although not totally
surrounded by leaves, it's more than 50%. As there is no earth connection
involved I guess the extra 30 ohms of loss is due to the dielectric properties of
the wood and leaves. 
 
Brian - G3YKB


Yahoo! Messenger NEW - crystal clear PC to PC calling worldwide with voicemail
<Prev in Thread] Current Thread [Next in Thread>