[AMRadio] Contactor

Geoff/W5OMR ars.w5omr at gmail.com
Sat Sep 15 23:21:04 EDT 2007

Geoff/W5OMR wrote:
> Either way, a millisecond or two is about all you
> need, and quite negligible.  Just make sure you have
> enough capacitor to discharge the resulting spark of
> Back EMF from the contacts, when the relay is
> actuated.

Er... that is to say, when the relay is 'relaxed', and no current 
flowing through it's coil, the contacts are closing a circuit.  It 
doesn't matter if it's AC or DC, you gotta get the resulting arc off of 
those relay contacts, otherwise, bye-bye relay.

I found this out the hard way, when I didn't put some sort of capacitor 
across the relay contacts of a PTT modification on one of my Viking 
II's.  Didn't take long for 600v @ 180mA to eat those contacts alive!

Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

73 = Best Regards,

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