Folks,
For a fast-acting relay, you might want to consider a Mercury Wetted type. The
Western Electric 275 and 276 relays have a switching time around 1 millisecond
and they have zero bounce on either make or break. They are rated to switch
and to carry 5 amps in telephone service. I use one to switch the antenna in
my CW QSK setup with a Heathkit SB-200 amplifier putting out about 600 watts
into my 50 ohm load - that's about three and a half amps through the relay. I
have the relay and the rig timed so that it carries but does not switch that
current. The WE 275 and 276 relays come in a can about the size of a 6AG7 tube
and have an octal base. If indeed they can handle 5 amps of RF, that would
amount to 1250 watts into 50 ohms. There are smaller WE Mercury Wetted relays
with a lighter-duty switch inside rated at 3 amps, one very common one being
the 337A. I use a 337A as an antenna relay with a Globe King that puts out 200
watts, 2 amps into 50 ohms, and it does just fine.
However with the 600 watts of my SB200, a 337A relay will stick closed. A
337A would be a good choice for a rig running at the 100 watt level. It is a
PWB mounting type with pins coming out the bottom of it's can. All of these
relays must be operated "upright" so that the liquid mercury inside will drain
down to the bottom of the switch. They also never "wear out." As I recall,
the C. P. Clare company which made a licensed copy of the WE relays had one
running on test, switching a load at a 60 Hz rate, for at least 10 years. That
would accumulate 18.9 billion operations.
You can usually find 275 and 276 relays on that e-place.
Jim, W8KGI
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|