[Amps] Alpha 9500 Relays Needed

[Jim Thomson]

Date: Thu, 23 Nov 2017 05:55:30 -0700
From: MU 4CX250B <4cx250b at miamioh.edu>
To: amps at contesting.com
Subject: Re: [Amps] Alpha 9500 Relays Needed

<Jennings RJ1A or the Kilovac HC1 relays are cheaper, widely available and
<make (IMHO) a superior alternative to the G41C in the Alpha 9500. They are
<about three times faster, have no contact bounce, and are much quieter.
<They mount in grommets and can be swapped for the G41C relays in minutes,
<without modifying the amplifier.

<Im curious about what happened to the original relays. What caused them to
<fail?

<73,
<Jim w8zr

## $ 650.00  for a pair of gigavac  G41Cs ??    Where the heck did he buy them from ? 
Allen Bond at max gain systems would have  the best prices on gigavac relays. 

##  Although a Jennings RJ1A  and a Kilovac HC1 relay will  work, another option
is the Gigavac  GH-1   The GH-1 is more robust than the  RJ1A  and HC1. 
A  GH-1  will easily high pot test  to 7.5 kv.   All  3 of em look identical, and have
identical specs. 

##  The gigavac  G41C  has  higher  V  +  RF current ratings at  DC, 2.5 mhz, 16 mhz,
and 32 mhz  vs the  RJ1A, HC1, and GH-1. 

##  But the V and current ratings  on the RJ1A,  HC1  and GH-1  are more than ample for
any 1.5 kw CCS amp, even on 10m.   The Gigavac  GH-1 easily handles 5 kw pep  on  6M
band. 

##  Other than lightning, I dunno how you would weld the contacts on a Gigavac G41C. 
If the swr is too high, or wrong or no ant is used, a simple, adjustable spark gap, wired in 
parallel with the output TR relay, will easily prevent the output relay from being damaged,
and ditto with the load cap in either a PI  or a PI-L amp.... + bandswitch.  
The gap is set, so the peak V required to arc the gap, is set a little higher than the highest
expected, worse case SWR.     IE:  like  4 or  5:1.    

##  In normal operation, the amp will have its own high swr protection, like 2.5:1  
or  3:1   External wattmeters like the AS  power master, etc, have adjustable SWR threshold
protection.   Exceed the high swr threshold in the amps built in high swr protection, and
the adjustable spark gap will fire.     The idea is to set the adjustable spark gap low enough,
so it protects the TR relay and load cap, buy higher than the worse case expected swr.

##  In actual use, the adjustable spark gap works slick.   I modeled it after the adjustable
contacts on my vibroplex keyer paddles.   It comes down to 2 points, made from  a pair
of SS  10-32 or  8-32 machine screws.  The ends of the machine screws are ground down to a fine
point.   One screw is fixed, the 2nd is adjustable.   One side to the TR relay... or hot side of a 
load cap on  simple PI net.    Other side is bonded to chassis.   IF the spark gap is wired 
directly to the hot side of the output coax connector, it will protect the output TR vac relay
on both TX..and RX.. + the load cap... and bandswitch. 

G41C info and specs http://www.gigavac.com/sites/default/files/catalog/spec_sheet/g41c.pdf

GH-1 info and specs  http://www.gigavac.com/sites/default/files/catalog/spec_sheet/gh1.pdf

Jim  VE7RF