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	<517ABCE1.8060802@iup.uni-heidelberg.de>
Date: Fri, 26 Apr 2013 17:47:51 -0400
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From: Warren Ziegler <wd2xgj@gmail.com>
To: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: Fire in the wire
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Hi Stefan,

       There are thousands or perhaps tens of thousands of volts from the
loop to ground.
If I grounded the loop with and there was a large potential difference,
wouldn't that cause a large current to flow to ground and effectively shunt
my signal to ground?

73 Warren



On Fri, Apr 26, 2013 at 1:44 PM, Stefan Sch=E4fer <
Stefan.Schaefer@iup.uni-heidelberg.de> wrote:

> Warren,
>
> What is the voltage between the tree (GND) and loop? I thought that the
> voltages are rather small, i.e. below 100V, especially when a large loop =
is
> used. Isn't it possible to ground the loop?
>
> 73, Stefan
>
> Am 26.04.2013 19:21, schrieb Warren Ziegler:
>
>
>> Just a quick report on a failure mode for LF TX antennas.
>> Last Fall my original TX loop made up of approximately 500 feet of RG-11
>> coax suspended from trees went open circuit (both center conductor and
>> shield), some time later part of the wire actually came down. I had thou=
ght
>> that abrasion from contact with the trees had eventually worn through it=
.
>>
>> What I found was a little more interesting. Looking at the downed end, i=
t
>> appeared that the insulation had melted for a considerable distance and
>> there were burn marks further up the cable. My hypothesis is that the ou=
ter
>> insulation was abraded away and the coax shield came into contact with t=
he
>> tree limb causing the burning/melting.
>> Will try to get some pictures this weekend and put them up on my website=
.
>>
>> Long term if one wants to operate at the kW level either better
>> insulation or a better way of supporting the antenna than trees would be
>> required!
>>
>> --
>> 73 Warren K2ORS
>>                 WD2XGJ
>>                 WD2XSH/23
>>                 WE2XEB/2
>>                 WE2XGR/1
>>
>>
>


--=20
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1

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<div dir=3D"ltr">Hi Stefan,<div><br></div><div style>=A0 =A0 =A0 =A0There a=
re thousands or perhaps tens of thousands of volts from the loop to ground.=
</div><div style>If I grounded the loop with and there was a large potentia=
l difference, wouldn&#39;t that cause a large current to flow to ground and=
 effectively shunt my signal to ground?</div>
<div style><br></div><div style>73 Warren</div><div style><br></div></div><=
div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Fri, Apr 26=
, 2013 at 1:44 PM, Stefan Sch=E4fer <span dir=3D"ltr">&lt;<a href=3D"mailto=
:Stefan.Schaefer@iup.uni-heidelberg.de" target=3D"_blank">Stefan.Schaefer@i=
up.uni-heidelberg.de</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">Warren,<br>
<br>
What is the voltage between the tree (GND) and loop? I thought that the vol=
tages are rather small, i.e. below 100V, especially when a large loop is us=
ed. Isn&#39;t it possible to ground the loop?<br>
<br>
73, Stefan<br>
<br>
Am <a href=3D"tel:26.04.2013%2019" value=3D"+12604201319" target=3D"_blank"=
>26.04.2013 19</a>:21, schrieb Warren Ziegler:<div class=3D"HOEnZb"><div cl=
ass=3D"h5"><br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
<br>
Just a quick report on a failure mode for LF TX antennas.<br>
Last Fall my original TX loop made up of approximately 500 feet of RG-11 co=
ax suspended from trees went open circuit (both center conductor and shield=
), some time later part of the wire actually came down. I had thought that =
abrasion from contact with the trees had eventually worn through it.<br>

<br>
What I found was a little more interesting. Looking at the downed end, it a=
ppeared that the insulation had melted for a considerable distance and ther=
e were burn marks further up the cable. My hypothesis is that the outer ins=
ulation was abraded away and the coax shield came into contact with the tre=
e limb causing the burning/melting.<br>

Will try to get some pictures this weekend and put them up on my website.<b=
r>
<br>
Long term if one wants to operate at the kW level either better insulation =
or a better way of supporting the antenna than trees would be required!<br>
<br>
-- <br>
73 Warren K2ORS<br>
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ<br>
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XSH/23<br>
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2<br>
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1<br>
<br>
</blockquote>
<br>
</div></div></blockquote></div><br><br clear=3D"all"><div><br></div>-- <br>=
73 Warren K2ORS<br>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ <br>=A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 WD2XSH/23<br>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2<b=
r>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1<br><br>=A0
</div>

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