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Re: [Amps] Kilovac relay in MFJ 2020 catalog

To: "'Jim Thomson'" <>, <>
Subject: Re: [Amps] Kilovac relay in MFJ 2020 catalog
From: "Jim Garland" <>
Date: Thu, 20 Feb 2020 17:27:26 -0700
List-post: <>
I've long wondered whether these speed-up circuits that pulse vacuum relay 
coils with an overvoltage also exacerbate contact bounce and possibly shorten 
the relay life. Intuitively that seems reasonable, though I've not taken any 
data to check out the possibility. A few years ago, I wrote up my personal QSK 
design and some of the accompanying relay data for QST (June 2015, and and at the time looked at the switching 
characteristics of numerous vacuum relays. I found a wide variation in the 
amount of contact bounce. The Gigavac G41C, used in the Alpha 9500,  typically 
had a half dozen or more bounces before the contacts settled down. That was a 
particularly noisy relay, with an audible twang when the movable contact 
slammed into its mating contact. The best relay, bounce-wise, was the Jennings 
RJ1A, which switched in about 2 msec, was nearly silent, and showed no bounce. 
There are various clones of the Jennings design, but I didn't check any of 
them. On the basis of the data, I chose the RJ1A for my "contest-rated" 160/80m 
duoband amplifier, and it's been great. (It's probably not hefty enough for the 
upper HF bands in that kind of application.)
Jim W8ZR

> -----Original Message-----
> From: Amps [] On Behalf Of Jim Thomson
> Sent: Thursday, February 20, 2020 08:51 AM
> To:
> Subject: [Amps] Kilovac relay in MFJ 2020 catalog
> Date: Wed, 19 Feb 2020 09:28:37 -0600
> From: Jim <>
> To:
> Subject: Re: [Amps] Kilovac relay in MFJ 2020 catalog
> <Depends on how fast the relay is. Just because its vacuum, doesn't mean
> <its fast!
> <I use solid state relays for cathode switching now days. Works great.
> <73
> <Jim W7RY
> ##  an  opto isolator  works,  along  with  its 4  kv  isolation.  Problem  
> is,  I  typ
> use  60-120  vdc  OCV  for  the  sped  up  26.5  vdc  vac TR relays....  +  
> drop
> resistor..+  small  cap  across  drop  resistor.   Kilovac  told  me  years 
> ago,  that
> if  voltage  limited,,  like  only  24 –27 vdc  available,  use vac  relays  
> with 12 vdc  coils.
> ##  Buddy  and  I  managed   to  speed  up a gigavac G2.....same  as a 
> jennings RJ2B.
> Rated  for  15 msecs   operate...and  9  msecs  release.   Sped  up,  with  
> 80  vdc
> and a .5uf  cap  across   drop  resistor,   they  become   2.5 msecs  
> operate..and  rls.
> 2nd  G2  was  2.7  msecs  operate  and  rls.   26.5 vdc  rated coils.
> ##  Both  G2s  were  individually tested on  bench.  Then  installed  in  GG  
> triode  amp,
> on  output  side,  with  all  contacts in  parallel.   Fast  enough  for  
> QSK,  and  good  for
> 20A  CCS  at  32 mhz.
> ## Ameritron  sez their  kilovac relay can be used  in  QSK.   Dunno  how u 
> can  do  that
> with a DPST relay.  Normally a DPDT  is  used...  or a SPDT  on   both input 
> +  output.
> ##  I  might  buy one....just  to  test on  the  bench....since  they  are  
> cheap.
> Jim  VE7RF
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