Re: Double Throw Spark Gap (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Mon, 15 Oct 2007 12:48:45 EDT
From: Mddeming@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: Double Throw Spark Gap (fwd)

 
In a message dated 10/15/07 10:23:34 A.M. Eastern Daylight Time,  
tesla@xxxxxxxxxx writes:

>  Also, I have another question somewhat unrelated to this thread, but
>  goes along with the University limits.  I obviously need an RF  ground,
> but I'm not allowed to pound anything into the ground.   So, I need a
> counterpoise.  I have virtually no idea on what is  acceptable here.  Is
> a 1 ft x 1 ft square covered in the middle  with many layers of chicken
> wire acceptable?
> 
>  Thanks,
> Chris B aka. Crispy


A counterpoise made of chicken  wire is a great idea.  But only one layer 
is needed, but it needs to  be bigger.  make its radius = height of 
topload above the  counterpoise.  So, if your coil is, say, a meter tall 
sitting on the  desk, the counterpoise should be about 2 x 2  meters.



Hi Crispy,
 
       If you have the room, a 2 meter  diameter circle for a one meter coil 
is about right. A foil counterpoise on a  cardboard stiffener would be 
cheapest, but would have the highest eddy current  losses. Chicken wire would have 
less loss, if you have someplace to keep it  flat. Again, cardboard base, 
perhaps with a hinged center for  storage. Radial wires have the least eddy current 
losses, and, if built  like a rimless wheel with many spokes attached to a 
small central ring, could be  collapsed like an umbrella for storage when not in 
use, but set-up time is  longer. 
    If you're going to hide an outdoor ground, try  driving a rod to just 
below ground level, excavate a small area around the  top big enough to put a 
pint jar over it and back fill when not in use.  When running, remove jar, attach 
ground lead with a removable clamp, (battery  cable clamp, or something 
similar) and you're good to go.
 
    I would not attach anything to University plumbing.  If they use 
insulated flanges anywhere in the system, you could be setting folks  up for a nasty 
surprise.
 
Hope this helps,
 
Matt D.



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