Conway,
The relay to test noise limiter, is wired to cut itself on and off through its
OWN contacts, continuously, to generate a noise spark across the contact from
the Inductive kick back voltage of the collapsing magnetic field around the
relay coil. Thus, the relay pulls in getting power first from the Normally
closed contact. Then, when it pulls; that contact opens, the relay coil has
no power, and the field around the coil collapses inducing a voltage spark at
the now open contacts. Almost simultaneously, with the opening contacts, the
spring of the relay pulls the contact back to the NC side, and the power is
again applied to make the coil pull the other way. Do you understand how that
works?
It is like a buzzer, on-off, on-off. This will make an excellent test signal
for a noise blanker. It is the way Ten Tec tests the one on the Scout/Argo.
Now, if you use a relay conventionally as a remote switch, you would not
generate noise, except perhaps upon make, or a long time later, break of the
relay contacts. And you can add back to back zener diodes across each arcing
contact to suppress the voltage, and keep the contacts from eventually
burning.
The zener will limit the amount of noise generated at a relay contact. Normal
use of a relay is to "throw a switch from a distance", and sometime later
throw it off, thus you are not continually generating noise.
Re-read the original post with these expaneded comments, and you will see what
he meant.
GL!
Stuart K5KVH
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