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Re: [TowerTalk] original source of "avoid sharp bends" in lightning

To: "'Jim Lux'" <>, "'Grant Saviers'" <>, "'towertalk'" <>
Subject: Re: [TowerTalk] original source of "avoid sharp bends" in lightning
From: "Barry Merrill, W5GN" <>
Date: Thu, 12 Apr 2012 09:19:07 -0500
List-post: <">>
I'm fairly certain that some of the earliest telegraph lines were curved
rather than bent because there was a belief the signals would go
straight if the turn was too sharp.

Barry, W5GN

-----Original Message-----
[] On Behalf Of Jim Lux
Sent: Thursday, April 12, 2012 8:32 AM
To: Grant Saviers; towertalk
Subject: Re: [TowerTalk] original source of "avoid sharp bends" in lightning

On 4/11/12 10:33 PM, Grant Saviers wrote:
> might be as simple as:
> "Don't do anything that increases the inductance of the grounding wire" ?

the original source might say that, but it's not actually true.  Until you
get a full 360 loop, the inductance of a bend isn't much more than the
inductance of the length of wire in the bend.

if you think about it, the increase in inductance in a loop is because the
magnetic field from one part of the wire interacts with the field from
another.  Two pieces of wire at right angles don't couple very well,
parallel pieces do.  A 360 loop has coupling "across" the loop, but with an
incomplete loop, much of the loop doesn't couple to anything else.

In any case, that's why I'm looking for the original source.  I suspect that
it's either:

1) how things were wired back in Ben Franklin's time, and it's carried on to
this day because it doesn't hurt, even if it doesn't help, either. 
  (the corollary, it takes more time to explain why not than to just do it)

2) A sharp bend produces a place where flashover/breakdown is more likely to

I discovered a few weeks ago that a bunch of the grounding conductor 
guidelines in power substations (something that amateur radio folks are 
unlikely to have to worry about) were based on the behavior of bolts and 
materials commonly used at the turn of the last century.  So that got me 

(that, and Ward's article about 468)

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