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Re: [TowerTalk] Coax Lengths for Stacked Yagis

To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Coax Lengths for Stacked Yagis
From: Richard Smith <n6kt1@sbcglobal.net>
Reply-to: Richard Smith <n6kt1@sbcglobal.net>
Date: Fri, 4 May 2018 16:15:01 +0000 (UTC)
List-post: <mailto:towertalk@contesting.com>
Hi Jim,
Thanks for your suggestions. Regarding the ceramic vac relays, do you use 
Jennings, Kilovac, or another manufacturer's relays?
Are the HV DPDT mechanical relays open-frame relays?  Is there a manufacturer 
that you like?
73, Rich, N6KT

      From: Jim Thomson <jim.thom@telus.net>
 To: towertalk@contesting.com 
 Sent: Friday, May 4, 2018 8:46 AM
 Subject: [TowerTalk] Coax Lengths for Stacked Yagis
   
<towertalk@contesting.com>
Subject: Re: [TowerTalk] Coax Lengths for Stacked Yagis


<I to am a supporter of having the phase box at the base of a tower. I am also 
subscribe to the notion of feed lines especially  after a switch box/phase box  
be ODD multiples of  ? wave

<Obviously taking the velocity  factor  into account. There has been more then 
one occasion where a phase box got hot switched and had to be changed out in 
the DARK.



<Wayne  W3EA

##  This is why I use ceramic vac relays.  Then the relays can go  anywhere on 
the tower, like at the midpoint of  a stack.  Hot switch all you want.  But 
they can also be set up so
they cant be  hot switched... like by using a break before make  type of  
rotary switch in the shack that controls the various relay configs. 
 
## Ceramic vac relays can also be used in plane jane remote switch boxes, like 
1-4 yagis, different bands etc, on a mast.  Remote switch box located on mast, 
then only 1 rotor
loop required.  Zero issues with moisture.    Then you can save coax..which is 
what I thought was the idea behind a remote switch box in the 1st place ?  If  
using mech relays,
the  HV DPDT types, with contacts in parallel, will provide for redundant 
contacts..and also double the current rating. 

##  But ceramic  vac relays are not cheap.... nor are  HV  DPDT mech relays.    
I put the ceramic vac relays inside a gasketed  water proof  fiberglass nema 
box, then also included
some silica gel...aka  dessicant,  and also a bit of heat, via 
paralleled..redundant  metal finned resistors, like the arcol brand, made in 
the UK.    No moisture ingress.  Unused ports
are  DC grounded. 

Jim  VE7RF
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