Date: Mon, 5 Sep 2011 19:30:44 -0400
From: "JE Brown" <W4LC@fuse.net>
Subject: Re: [TowerTalk] Remote Antenna switch - additional
Also, running a business card lightly sprayed with contact solvent between
the contacts occasionally will be beneficial.
Jim W4LC
%%% I have the 15 kw version of the AS rat pack. It uses DPDT relays,
big ones, but they are open frame types..with 20 A contacts. I silver plated
the contacts with
....cool-amp..... then applied a THIN layer of ...conducto-lube.
Conducto-lube
is just grnd up silver powder... in grease. Both products are made by the same
co in
Ore... cool-amp.com . AS can also make the same 15 kw rat packs..but with
DPDT 30 A
contacts. Mine is a simple, one in and six out ant switch box. All
DE-energized ports
have their center conductor`s DC grnded. You end up with loads of port to
port isolation
with this scheme. The Un- used ports, with their center conductors dc grnded
to the case
won`t be passing along signals any time soon. I have also seen them in 1 in,
9 out versions.
%%% By using DPDT relays, you have double the RF current capability..and also
quadruple
the power handling capability. You also end up with redundant contacts ! AS
just parallels all the
contacts of the DPDT relay..so you end up with one big SPDT relay. COM-COM
NC-NC
NO-NO Between the DPDT relays..and the use of the cool-amp glop and also
conducto lube
glop... you will not have problems with things going int on you in the middle
of winter.
%%% Now if you really want 120% bomb proof.... then use vac relays..either
surplus or new.
I used gigavac brand.... model G-2s from Allen Bond at max gain systems
for my 40m cw +ssb
switching arrangement. You can get them in either 12 vdc or 26.5 vdc coil
versions. They are
sealed from the WX.....permanently, never go int on you..and handle globs of
power. A gigavac
GH-1 will also work. Both are SPDT types. The G-2 vac relays I use have
threaded inserts, and
mating silver plated machine screws instead of the solder version. This is
for the COM-NC-NO
contacts. Now this allows the use of either sta-kon crimp and solder
connectors on the ends of wires..
and OR using copper strap. I also silver plate all copper strap with cool
amp glop.
%%% If you want 1000 % bomb proof.... then use DPDT vac relays. Unlike
other`s... I don`t want
any remote switch box at the base of a tower, I want it at the top..the idea
being so save coax. One good run
of big diam coax up the tower to the remote box input. Then smaller, flexible
stuff to each ant. Don`t forget to add
the gas discharge tube to the remote switch box input. Or a stand alone gas
discharge tube can be added externally
to the input of the remote swuitch box. I also include a heavy duty coil,
between input and casing..so the active ant
also has it`s center conductor DC grnded. Then all the braids of the 6
outputs arer effectively bonded to the
top of the tower.......via the casing of the remote switch box. The braid of
the main coax is also bonded to the base of the
tower..via a HOFI brand lightning discharge gas tube bulk head unit. This
also serves as an interface between the bigger, rigid
coax from shack to base of tower..and the slightly smaller coax running up the
side of the tower. A 3rd protector is used
on the SPG... just inside the basement wall.... mounted to a .25 inch thick
sheet of 6061-T6 AL plate.
later......... Jim VE7RF
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