[TowerTalk] Remote Antenna switch - additional

[Jim Thomson]

Date: Mon, 5 Sep 2011 19:30:44 -0400
From: "JE Brown" <W4LC at 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