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From: Andy Talbot <andy.g4jnt@gmail.com>
Date: Fri, 23 Jun 2017 15:58:25 +0100
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Take care lads, grass fire here...
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Never use nylon as an RF insulator,  it's horribly lossy.  Back in the
73kHz days I used nylon strimmer cord  as an insulator for my Tee antenna;
200Watts and about 15kV on the antenna.  One day , in wet weather, after a
prolonged transmission Pout suddenly dropped and I saw the antenna had
fallen down.   The nylon had just melted.  Presumably a combination of
lossy material and damp helping tracking.

Replaced with a decent ceramic dog-bone at each end and its been fine ever
since - nearly 20 years

Andy  G4JNT

On 23 June 2017 at 15:50, John Andrews <w1tag@charter.net> wrote:

> Chris,
>
> I recall throwing snowballs at a flaming tree one winter evening. Small
> fire -- mostly the insulation on the wire for my loop antenna. But the tree
> bark had definitely joined the blaze.
>
> So, it's not just hot, dry wx. LF and fire are close friends.
>
> John, W1TAG
>
> On 6/23/2017 10:10 AM, Chris Wilson wrote:
>
>> Hello LF`ers,
>>
>>      Just made a quick test WSPR TX here and the wind has got up here.
>>      First TX was fine, second one, luckily whilst I was watching the
>>      Scopematch, suddenly went odd. Shut it down and went outside, to
>>      find the nylon fishing line tether for the vertical wire had
>>      broken and the vertical had set light to the dry grass strimmings
>>      near the loading coil. Luckily I managed to stamp it out otherwise
>>      the green wheelie bin with the loading coil in it would have
>>      caught too. Deep scorch marks on a wooden post that stops the
>>      wheelie bin blowing over as well, from arcing from the vertical
>>      wire. Take care in this dry weather especially if the wind gets
>>      up..... :)
>>
>>
>

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<div dir=3D"ltr">Never use nylon as an RF insulator, =C2=A0it&#39;s horribl=
y lossy.=C2=A0 Back in the 73kHz days I used nylon strimmer cord =C2=A0as a=
n insulator for my Tee antenna; 200Watts and about 15kV on the antenna.=C2=
=A0 One day , in wet weather, after a prolonged transmission Pout suddenly =
dropped and I saw the antenna had fallen down. =C2=A0 The nylon had just me=
lted.=C2=A0 Presumably a combination of lossy material and damp helping tra=
cking.<div><br></div><div>Replaced with a decent ceramic dog-bone at each e=
nd and its been fine ever since - nearly 20 years<br><div><br></div><div>An=
dy =C2=A0G4JNT</div></div></div><div class=3D"gmail_extra"><br><div class=
=3D"gmail_quote">On 23 June 2017 at 15:50, John Andrews <span dir=3D"ltr">&=
lt;<a href=3D"mailto:w1tag@charter.net" target=3D"_blank">w1tag@charter.net=
</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin=
:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Chris,<br>
<br>
I recall throwing snowballs at a flaming tree one winter evening. Small fir=
e -- mostly the insulation on the wire for my loop antenna. But the tree ba=
rk had definitely joined the blaze.<br>
<br>
So, it&#39;s not just hot, dry wx. LF and fire are close friends.<br>
<br>
John, W1TAG<br>
<br>
On 6/23/2017 10:10 AM, Chris Wilson wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
Hello LF`ers,<br>
<br>
=C2=A0 =C2=A0 =C2=A0Just made a quick test WSPR TX here and the wind has go=
t up here.<br>
=C2=A0 =C2=A0 =C2=A0First TX was fine, second one, luckily whilst I was wat=
ching the<br>
=C2=A0 =C2=A0 =C2=A0Scopematch, suddenly went odd. Shut it down and went ou=
tside, to<br>
=C2=A0 =C2=A0 =C2=A0find the nylon fishing line tether for the vertical wir=
e had<br>
=C2=A0 =C2=A0 =C2=A0broken and the vertical had set light to the dry grass =
strimmings<br>
=C2=A0 =C2=A0 =C2=A0near the loading coil. Luckily I managed to stamp it ou=
t otherwise<br>
=C2=A0 =C2=A0 =C2=A0the green wheelie bin with the loading coil in it would=
 have<br>
=C2=A0 =C2=A0 =C2=A0caught too. Deep scorch marks on a wooden post that sto=
ps the<br>
=C2=A0 =C2=A0 =C2=A0wheelie bin blowing over as well, from arcing from the =
vertical<br>
=C2=A0 =C2=A0 =C2=A0wire. Take care in this dry weather especially if the w=
ind gets<br>
=C2=A0 =C2=A0 =C2=A0up..... :)<br>
<br>
</blockquote>
<br>
</blockquote></div><br></div>

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