Content-Transfer-Encoding: 8bit
Message-ID: <3617AC3245C2D1118A840000F805359C01AB8CE6@pdw-mercury-1.dera.gov.uk>
From: "Talbot Andrew" <ACTALBOT@dera.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: RE: LF: Wire, for LF Antennas
Date: Fri, 30 Jun 2000 08:37:29 +0100
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

There is also the issue of reduced skin depth and extra losses when
using steel wire, or any other magnetic material for that matter.   Skin
depth reduces as the square root of relative permeability, which for
steel wire is several thousand.

Did the modelling of the MF atnennas take this magnetic wire effect into
account, although at those frequencies much of the current will be
concentrated in the zinc galvanising so reducing the Ur losses.

As you say, the high impedance of these antenna will not show up the
losses in the wire nearly as much as using steel wire at LF where skin
depth is 0.2mm or so.

Andy  G4JNT


> ----------
> From: 	vernall[SMTP:vernall@xtra.co.nz]
> Reply To: 	rsgb_lf_group@blacksheep.org
> Sent: 	2000-06-30 07:46
> To: 	rsgb_lf_group@blacksheep.org
> Subject: 	Re: LF: Wire, for LF Antennas
> 
> Larry,
> 
> Mentioned for completeness, at the Quartz Hill ZL6QH DX station, of
> which I am a member, we decided to use high tensile 12 gauge
> galvanised
> steel wire for replacement of any of the long Vee antennas.  Legs are
> typically 250 to 300 metres long.  We modelled the situation and found
> that losses were only fractional compared to using hard drawn copper. 
> Some have been installed for over a year, and Wellington has a
> reputation for being "Windy Wellington".  The 12 gauge high tensile
> galvanised steel wire is in regular use for fences on New Zealand
> farms,
> so is cheap and available.
> 
> The ZL6QH Vees are all fairly high (surge) impedance wires at the
> MF/HF
> bands and that is why a few more ohms of surface resistance does not
> give rise to a significant loss factor.
> 
> An LF antenna may well be a low resistance affair where series
> resistance in the "top loading" is significant, at least for
> transmitting efficiency.  I think another reply on the reflector
> mentioned using copper for an "upwire" and galvanised steel for the
> top
> loading.  In terms of "bang for buck" it could pay to concentrate on a
> higher upwire than wider top loading.
> 
> 73, Bob
> 
> 


-- 
The Information contained in this E-Mail and any subsequent correspondence
is private and is intended solely for the intended recipient(s).
For those other than the recipient any disclosure, copying, distribution, 
or any action taken or omitted to be taken in reliance on such information is
prohibited and may be unlawful.