Railroad Track ground

To: mail11: ;
Subject: Railroad Track ground
From: pierson-at-msd26.enet.dec-dot-com
Date: Tue, 9 Jul 96 13:08:51 EDT
Cc: pierson-at-msd26.enet.dec-dot-com
[Others have had some good advice. let me toss in some.  FWIW, i have a
LARGE shelf of books on rr track circuits, etc...

>Anybody have an opinion on the suitabilty of a abandoned,
	Important.  Operating track should be avoided for a variety of
	safety reasons, yours and theirs.  The track circuits will likely
	not be hurt (the associated gear is designed to withstand lighting
	strikes....8)>>), but it may be incapacitated during tesla operation.

	And how far is it from here to the nearest operational section?

>partially buried
	How partially?  (and, as others have pointed out, in what kind of
	ground?)

>railroad track as a ground?
	It may not be obvious, but track circuited rail is NOT grounded.
	It is specifically insulated...

>We're planning on renting out the coil for a video shoot in downtown Los 
>Angeles (the scummy industrial part)
	Rail spurs are commonly not track circuited, meaning no bondwires
	around the track joints....

>and the ground at the site is to hard or asphalt covered
	Likely make a lousy gound to the buried rails then, conductively.

>to bury copper poles and flashing. We are thinking of drilling and tapping a
>3/8" ground lug on one of the nearby railroad tracks which is partially
>uncovered (the rest is buried under the street).
	Be REAL sure as to isolation from operational rail segments.  There are
	some nasty federal laws on interference (8)>>) with RR signalling.

	My guess:

	It would work ok.  It might not:
	bad joints, bad 'ground', but since the RF is happy with a capacitive
	coupling, that means that a _large_ structure, even if not conductively
	coupled might be ok.  More as a 'counterpoise', perhaps (as noted by
	others) than as a ground, per se.

	I'd be tempted to do at least two connections, one to each rail.

>Any thoughts?...   ...Jeff Parisse
	Someone else suggested a test.  A signal generator and scope or good
	ac/rf voltmeter and see what 'currents' flow to some 'other' ground.
	Maybe a small coil, and see if it reacts to being connected to the
	proposed ground, by varying its 'tune'.  If it does NOT react, then
	the proposed 'ground' is probably a 'bad' one....

	regards
	dwp