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Date: Thu, 27 Jan 2011 15:06:16 +0000
Message-ID: <AANLkTinbxcRAqcrTiYYLVv2qm1N4BRiaTscLACth_ao8@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: LF: Advisory / Warning
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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

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<div>Thought I&#39;d better warn QRO LF ops about this - something that ha=
d never occured to me before, and could be nasty.</div>
<div>=A0</div>
<div>I&#39;m laying=A0floor panels in my loft space, and this involves rer=
outing 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.=A0 Anyway, there I was, was happily threading twin-and-earth ca=
ble=A0by torchlight (*) when I suddenly got a nasty RF burn holding one en=
d of a piece</div>

<div>=A0</div>
<div>The 500kHz WSPR beacon is running, and the bit I was holding was isol=
ated from the house main earth wire.=A0=A0The Tee antena runs outside over=
 the roof,=A0only 3m or so away from where I was working.=A0=A0 So more th=
an enough pickup with me and a bit of wire forming a dipole in the near fi=
eld of 4kV at 500kHz</div>

<div>=A0</div>
<div>Now, bearing in mind the burnt ATU cabin of a few months ago, it made=
 me think...</div>
<div>Large bits of bare isolated wire or metal in roof spaces where LF ant=
ennas pass over could be risky.=A0=A0 They could pick up enough voltage to=
 spark - and if there&#39;s paper/ wood / plastic at the sparking point,=
 an RF spark that always seems to turn into an arc, is very hot.</div>

<div>=A0</div>
<div>Just a thought.</div>
<div>=A0</div>
<div>(*)=A0and BTW,=A0there is a very strong argument for <u>not</u> havin=
g your roofspace light on the same circuit as your normal upstaris lightin=
g</div>
<div>=A0</div>
<div>Andy</div>
<div><a href=3D"http://www.g4jnt.com/">www.g4jnt.com</a></div>
<div>=A0</div>

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