RE: simple question RF gnds

To: tesla-at-pupman-dot-com
Subject: RE: simple question RF gnds
From: Dale Hall <Dale.Hall-at-trw-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Thu, 02 Dec 1999 12:30:25 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Leslie,

RF grounds:
Current carrying capability is inversely proportional to impedance
Z=Rdc+(XL-XC).
Ground wires possess inductance so Z=R+(XL-XC) increases with frequency
XL=2piFL = degrading ground
  assume wire capacitance to ground is trivial, 
    (note of interest: using a large area ground/counterpoise beneath your
Coil
     possessing a large surface area and over a good ground 
     (moist grass/soil/body of water/cement) 
     increases effective grounding by means of a large shunt (parallel)
Capacitance XC=1/(2piFC) )

Wire resistance at DC is a constant and very low,
Effecting a low Z (impedance) requires using a large surface area due to 
skin affect conduction occurring only around a thin surface area of metal
conductors
  (one reason the Pri can be "hollow" copper tubing - solid center
contributes little)
   becoming more important as frequency increases 
   (note the "frequency" may not be obvious i.e. it relates to that of the
highest freq component 
    occurring say, in a discharge or a spark gap, 
    each possessing much higher freq's than TC pri/sec resonant freq's)

so wide copper straps (silver coated=very best) are preferred followed by 
   Litz wire (lots of insulated wires bundled together effecting a large
surface area)

Electrical grounds: assuming DC or equivalent
conductor current ability is related to its DC resistance (no AC reactance
to consider)
Solid conductors of any shape provide low DC resistance proportional to
cross-sect area.

Z increases for single round wires as frequency increases 
causing the center cross sect area to carry less of the total current
thereby degrading ground effectiveness.

Regards, Dale

-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, November 30, 1999 5:23 PM
To: tesla-at-pupman-dot-com
Subject: simple question

Original Poster: LEST2001-at-aol-dot-com 

This is such a simple question I'm embarrassed to ask, but everyone has been

so helpful. What is the difference between RF ground, and an electrical 
ground?   
Thank you,
Leslie