[Amps] Kilovac relay in MFJ 2020 catalog

[Jim Garland]

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 http://www.w8zr.net/QSK/). 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.)
73,
Jim W8ZR

> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Jim Thomson
> Sent: Thursday, February 20, 2020 08:51 AM
> To: amps at contesting.com
> Subject: [Amps] Kilovac relay in MFJ 2020 catalog
> 
> Date: Wed, 19 Feb 2020 09:28:37 -0600
> From: Jim <jimw7ry at gmail.com>
> To: amps at contesting.com
> 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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