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Re: Many Things...

At 05:27 PM 7/27/99 -0600, Tesla List wrote:
>Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov> 

Hi Jim, All,

>> Now that's an interesting point - Does high altitude make a significant
>> difference for the gap setting?
>
>> 
>> You're at the top of the state, but I'm at the midpoint (Crestone, Sangre
>> de Cristo mountain chain, 50 miles south of Salida) and the altitude
>> here is 8000 feet. 
>
>YES... as a rule of thumb, breakdown voltage for a given gap varies
>linearly as the pressure.  Since the pressure at 8000 feet is about 73%
>that of sealevel, the breakdown voltage will be 73% of the sealevel
>breakdown, for the same gap length.

Would I be correct in presuming that if I was to ever move back down 
to sealevel I would have to re-adjust the gap settings I have set at 
high altitude?

 >> I'm also curious what kind of grounding system you use for your coils
>> in this rocky, dry soil of Colorado?
>
>The grounding system is really only relevant in the near field of the TC...
>You want a low impedance (high conductivity) ground to serve as the other
>"plate" of the top load.  If you were to have a plate the diameter of which
>was twice the height of the top of the TC above it, it would probably work
>pretty well.  

Terry replied he used water pipe. The problem I have is hard soil and it's
a challenge to sink a copper rod deep enough without hitting a boulder. This 
(San Luis Valley) region is part of a former glacier and there are rocks as
big as a house here. I do have an old metal sign that is 4' in length by 3' in 
width. If I was to bury this sign and sink a copper rod or water pipe through
the middle, barring hitting any rocks, would this increase the ground plane 
enough without having to sink several additional rods? Could I use the large 
metal area of the sign by itself as an equipoise and would this do the 
trick?

I appreciate yours and others responses on this as it's been somewhat of a
vexing issue to resolve. If I still lived in Florida, this wouldn't be a
problem
at all. Sinking a rod most places in Florida is a breeze and chances are real
good you'll hit water at a very minimum depth. 

Don



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"Resistance to tyrants is obedience to God" - Thomas Jefferson