[TowerTalk] Lightning suppression through coax loops

[Jim Thomson]

Date: Thu, 27 May 2010 08:09:51 -0400
From: Pete Smith <n4zr at contesting.com>
Subject: [TowerTalk] Lightning suppression through coax loops


I bought an Ameritron RCS-10 antenna switch at Dayton, and in reading 
the manual (please, no giggling) I note that it calls for a two-turn 
loop in each antenna coax line just before entering the relay box. 
These are described as "drip and lightning retarding loops." The manual 
is quite prescriptive (for example, "keep coils spaced from each other 
by vertical or horizontal separation of 2" minimum"), and I get the 
"drip" part, but I wonder what the real, practical effect of these loops 
would be.  Is there enough inductance to offer any practical blocking 
effect for induced voltages resulting from a nearby strike?

73, Pete N4ZR

## I have the AS  rat pack... 1 in 6 out box... and the 6x connectors are all
on the bottom..... so one still requires a loop  to get from above the box... to below
the box..      I was planning on mounting mine abt 2'  up the mast. So just the bottom yagi
won't require any loop.... but water can't flow up hill  so no big deal.  Since the yagi's  above
the box all require loops anyway... there is your drip loop by default. 

##  while on the subject of lightning arrestors...is there any point to installing one  at the INPUT
of a remote switch box.. at the TOP of a tower ???  Any yagi with a hairpin [F-12] has it's center
conductor bonded to braid side anyway.   Since the remote switch box is 2' up the mast.. that means BOTH
the braid + center conductor of all yagis gets DC  grnded at the mast [via switch box] . 

## The only exception is the one yagi  with the 50 ohm direct feed. [17/15m array...F-12  N1715XL] 
 It has a bead balun.. and nothing else. In that case, the braid gets DC grnded at the remote switch box....
but the center conductor does not.   I was thinking perhaps a  20-35 uh choke..say  8 ga polyimide magnet
wire... could be wired directly across the DE terminals ???    OR  from center conductor side of DE...to
boom ??     Then at least the DE  ends up dc grnded.   Will this work..or will the 20-35 uh choke screw
things up ??  35 uh = 4681 ohms XL  @ 21.3 mhz.   45 uh = 6019 ohms

later... Jim   VE7RF