Date: Thu, 23 Nov 2017 05:55:30 -0700
From: MU 4CX250B <4cx250b@miamioh.edu>
To: amps@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
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