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Date: Thu, 26 Sep 2013 13:34:04 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: TA CW?
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Hi Bob,

Am 26.09.2013 01:00, schrieb Bob Raide:
> Stefan;
> What kind of ground system do you use
For me it was quite easy, i simply use the lightning protection system 
of building so i just needed to connect the cold end of the coil to that 
wire on the roof. Some of the walls of the building are metallic and are 
connected to that earth system. The result is incredible!

> and recommend?
As Alan says, it depends on your local situation. But usually ground 
rods are better than radials, or more "efficient" (effort and result). 
You have to measure what happens when you make a change in the system. 
Then you see if it is worth to continue (e.g. adding another earth rode 
in some distance).

Give me some more details. Now you're getting 9.5A antenna current at 74 
kHz and 1.5 kW? That would be 16 Ohm total loss resistance, which is 
quite good. And for 74 kHz, i assume your coil will cause a significant 
part of the losses. What type of loading coil do you use? Photos? You're 
only using that chicken wire and the well?

> How you can confine all that power in such short ant!!!  That 
> insulator burns with that little flame all the time you transmit-rain 
> or shine?
The insulator is ceramic and will survive every dirty experiment i'm 
doing. No, there is no arcing any more since i applied that spheric 
electrode (4 cm diameter) there. The arrangement acts as a spark gap in 
case of a direct lightning strike, to protect the loading coil. The 
lightning impulse withstand voltage of that spark gap (in the range of 
80 kV  1.2/50) is lower than the one of the coil, so the coil will be 
protected...

73, Stefan

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Hi Bob, <br>
<br>
Am 26.09.2013 01:00, schrieb Bob Raide:
<blockquote cite="mid:BLU180-W691AC260F75F27A648E24AC2F0@phx.gbl"
 type="cite">
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  <div dir="ltr">Stefan;<br>
What kind of ground system do you use</div>
</blockquote>
For me it was quite easy, i simply use the lightning protection system
of building so i just needed to connect the cold end of the coil to
that wire on the roof. Some of the walls of the building are metallic
and are connected to that earth system. The result is incredible!<br>
<br>
<blockquote cite="mid:BLU180-W691AC260F75F27A648E24AC2F0@phx.gbl"
 type="cite">
  <div dir="ltr"> and recommend? <br>
  </div>
</blockquote>
As Alan says, it depends on your local situation. But usually ground
rods are better than radials, or more "efficient" (effort and result).
You have to measure what happens when you make a change in the system.
Then you see if it is worth to continue (e.g. adding another earth rode
in some distance). <br>
<br>
Give me some more details. Now you're getting 9.5A antenna current at
74 kHz and 1.5 kW? That would be 16 Ohm total loss resistance, which is
quite good. And for 74 kHz, i assume your coil will cause a significant
part of the losses. What type of loading coil do you use? Photos?
You're only using that chicken wire and the well? <br>
<br>
<blockquote cite="mid:BLU180-W691AC260F75F27A648E24AC2F0@phx.gbl"
 type="cite">
  <div dir="ltr"> How you can confine all that power in such short
ant!!!&nbsp; That insulator burns with that little flame all the time you
transmit-rain or shine?</div>
</blockquote>
The insulator is ceramic and will survive every dirty experiment i'm
doing. No, there is no arcing any more since i applied that spheric
electrode (4 cm diameter) there. The arrangement acts as a spark gap in
case of a direct lightning strike, to protect the loading coil. The
lightning impulse withstand voltage of that spark gap (in the range of
80 kV&nbsp; 1.2/50) is lower than the one of the coil, so the coil will be
protected...<br>
<br>
73, Stefan<br>
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