[TowerTalk] Coax Lengths for Stacked Yagis
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.
## 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.
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