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[TowerTalk] Gas Tube protection for remote antenna switches;

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Subject: [TowerTalk] Gas Tube protection for remote antenna switches;
From: "Jim Thomson" <>
Date: Mon, 26 Jul 2010 05:46:46 -0700
List-post: <">>
Date: Mon, 26 Jul 2010 06:21:30 -0400
From: Pete Smith <>
Subject: [TowerTalk] Gas Tube protection for remote antenna switches;
shorting coax cables when disconnected

Yesterday we had a severe thunderstorm episode, with significant 
cloud-to-ground lightning nearby.  All my coax and control lines were 
disconnected, but when one particularly close strike occurred, an arc 
jumped across the open SO-239 on my entry panel.  No damage in the 
shack, fortunately, but it set me wondering.

1.  Does it make sense to put a shorting plug at the shack end of a coax 
cable?  With my Ameritron RCS-10 relay box, putting a shorted PL-259 in 
position 1 on the relay box has the same effect when the control cable 
is disconnected, except at the tower end.  A better idea?

##  putting a shorted pl-259  in pos #1  just used up pos #1. 
Why not use a torroid.. like 45 uh... using 10-12 ga magnet wire. Then,
the center conductor is always at DC grnd.  [ on the cable heading towards
the station.. ie:  input side]  

## does the ameritron  grnd, or float the un-used ports ??   My AS
box grnds all the unused ant ports.    DPDT relays  are used, one per
port.  Common  goes to ant port,  NC  goes to grnd buss... and NO
goes to kw input buss.     If lightning present, all Unused ports are grnded.
If power to control box is shut off, or rotary switch thrown to pos 7-12.. then
all  ports  1-6  are grnded.   

## You could also install an ICE arrestor, or similar, at shack end... then
the center conductor is always DC it has a gas discharge tube
in parallel with the  12 ga , 35 uh torroid they use.   It's also dc blocked... 
 the station side of the block caps has series resistors  going to grnd.   You 
also install a 2nd torroid on the station side of any dc block cap. 

##  I'd also grnd all the braids if all coax cables   at the top of the 
then run the coax down the inside of the tower .. and also grnd the braids  at 
base of 
tower.    Then install the ICE  arrestor or eq in the station. 

##  IF the yagi uses  either a hair pin  [floating]    or a beta match [ grnded 
hair pin]  then the
center conductor is grnded anyway.   If no hair pin is used... like on an OWA  
design.... I see no reason
why a  35-70uh   choke couldn't still  be used  directly across the DE.   If a 
remote switch box is used, at least you have
all the braids grnded at top of tower already. 

2.  Ameritron makes a "lightning-protected" version of the RCS-10, 
called the RCS-10L.  From the parts list (no schematic) it appears that 
the only added component is a gas tube, rated at 1500V, 10 KA.  I 
presume this is across the output of the relay box coming to the shack.  
Again, good idea?

##  sure, that will work.   But can u take the box apart to change out the
gas discharge tube, with no hassle ?   On the German Hoffi brand lightning
arrestor's,   it takes no time at all to change out the gas discharge tube.  
deal with the Suhner + also the Spinner brand of lightning arrestor's. 

## did Ameritron install the gas tube on the side of the remote box... for easy 
access ? 
1500 V    means the gas tube is good for  20 kw  with flat swr... and 10 kw  
with  a 3:1 swr. 

Later... Jim  VE7RF  
73, Pete N4ZR


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