Vacuum Relay contact Bounce.
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A year or two back, I used the RJ1A, the HC-1 and
a few larger vacuum relays in a research project.
=
Although these relays established contact transfer
in the reported < 2ms time, there was considerable
contact bounce.
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Contact bounce made the tested relays unusable
for at least a few milliseconds. The best I could
get from the HC-1 was ~4 ms without repeated
contact bounce. I consider the 1.5ms speed to
be a little to optimistic.
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cheers
skipp
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--------- Forwarded message ----------
From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
The RJ1A is rated at 8 milliseconds max open or close, and the Kilovac
HC-1 at 6ms max. The GH1 is rated at 6ms but it doesn't say whether this
is maximum or typical.
All these figures are when operated from the rated coil voltage, and
neither speeded-up nor slowed-down electrically.
Rich's highly successful circuit uses a high-voltage supply and a series
resistor. Recalling earlier posts from Rich, this will speed up typical
24V relays (RJ1A and HC-1) to about 1.5ms closing. This level of speed
means that relay closing time is not a significant factor in your QSK
timing.
However, you don't actually *need* a high voltage supply to achieve this
speedup. You can do almost the same from the existing relay voltage, by
using the one-transistor circuit developed by K1KP. Using this circuit
with the normal 24V rail, I've had 1.5ms closure times from a number of
HC-1 relays... pretty much the same as Rich gets.
Adding a 'universal' 12V low-current PTT interface to any transceiver,
the circuit expands to a whole three transistors - see:
http://www.ifwtech.co.uk/g3sek/in-prac/best-of.htm#speedup
Click on the "April 2002" link for more details of how it works.
It's an easy mod to almost any amplifier, and will also speed up an
existing open-frame antenna relay. Bringing the closure time down from
about 30ms to more like 15ms can sometimes cure hot-switching problems
without needing to change the relay.
BTW, my favorite source for vacuum relays is:
http://www.mgs4u.com/relay.htm
Allen Bond is a straight guy, and very easy to deal with.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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