[TowerTalk] Coax Lengths for Stacked Yagis

Jim Thomson jim.thom at telus.net
Fri May 4 11:46:05 EDT 2018

<towertalk at 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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