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