From: g4gvw <g4gvw@aol.com>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <D7179B21BB8A45989B7891644F3680D1@Hugh>
References: <AANLkTinbxcRAqcrTiYYLVv2qm1N4BRiaTscLACth_ao8@mail.gmail.com>
	 <D7179B21BB8A45989B7891644F3680D1@Hugh>
Date: Thu, 27 Jan 2011 18:40:14 +0000
Message-Id: <1296153614.16768.7.camel@pat-compaq-evo>
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Subject: Re: LF: Re: Advisory / Warning
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It, also, raises an interesting point about the merits and demerits of
routing mains cabling in metal conduits (earthed/grounded). On the one
hand you have a shielded system which, assuming the drop to the house is
SWA leaves only minor parts to radiate or pick up interfering sigs. The
downside of course being the grounded metal framework.................

Food for thought and discussion perhaps?

73


On Thu, 2011-01-27 at 15:29 +0000, Hugh_m0wye wrote:
> If you had a few spare fluorescent tubes lying around you probably wouldn't 
> have needed the torch - I understand Nicola Tesla illuminated his workshop 
> in this way :-)
> 73
> Hugh M0WYE
> 
> ----- Original Message ----- 
> From: "Andy Talbot" <andy.g4jnt@gmail.com>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Thursday, January 27, 2011 3:06 PM
> Subject: LF: Advisory / Warning
> 
> 
> > Thought I'd better warn QRO LF ops about this - something that had never
> > occured to me before, and could be nasty.
> >
> > I'm laying floor panels in my loft space, and this involves rerouting some
> > of the upstairs lighting wiring - drilling holes and feeding the wire 
> > though
> > rather than it laying on top of joists where the flooring will sit. 
> > Anyway,
> > there I was, was happily threading twin-and-earth cable by torchlight (*)
> > when I suddenly got a nasty RF burn holding one end of a piece
> >
> > The 500kHz WSPR beacon is running, and the bit I was holding was isolated
> > from the house main earth wire.  The Tee antena runs outside over the
> > roof, only 3m or so away from where I was working.   So more than enough
> > pickup with me and a bit of wire forming a dipole in the near field of 4kV
> > at 500kHz
> >
> > Now, bearing in mind the burnt ATU cabin of a few months ago, it made me
> > think...
> > Large bits of bare isolated wire or metal in roof spaces where LF antennas
> > pass over could be risky.   They could pick up enough voltage to spark - 
> > and
> > if there's paper/ wood / plastic at the sparking point, an RF spark that
> > always seems to turn into an arc, is very hot.
> >
> > Just a thought.
> >
> > (*) and BTW, there is a very strong argument for *not* having your 
> > roofspace
> > light on the same circuit as your normal upstaris lighting
> >
> > Andy
> > www.g4jnt.com
> > 
> 
> 
-- 
73 es gd dx de pat g4gvw
 qth nr felixstowe uk
(east coast, county of suffolk)