Tom writes:
>Of course it never hurts to measure an unknown, but virtually all
>relays useful in amplifiers take far less than 20ms to switch.
>Typical open frame 20 ampere relays switch in 12 mS or less. The
>only relays I have seen that are near 20mS are large contactors. Of
>course one has to be sure the coil voltage is at least the rated
>voltage.
>Another problem often overlooked is the drop times. That can be
>fatal!
I spent an afternoon measuring different relay latch and drop times
using a test setup with 10KHz pulses and HP counter. The project
was to modify the WX0B Stack Matcher to transmit using all the
antennas and receive on only the selected one. The modification
requires the RF to be off until the Stack Matcher drop time is complete.
The relays in the WX0B Stack Match are Nvis JW1FSN high power relays
that latch and drop out in about 4 to 6 mS. A standard off the shelf rat shack
12 vdc PC relay (275-249) runs around 7 mS. The standard RF coaxial relays
bounce around 12 to 14 mS. I built a simple "double the DC voltage to the
coil circuit" to see if I could improve this time and knocked off a big 2 mS.
They could also be made faster by moving the contacts closer to the wiper,
the ones I had here on the bench were set rather wide.
73 Rich KL7RA
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