[Elecraft] K3 external qro keying line
Paul Christensen
w9ac at arrl.net
Thu Feb 12 11:04:05 EST 2009
> "Unless you are running QSK and need instant keying, I would suggest adding a small 12v relay inside the K3 that the solid state device keys and presents the user with a set of dry, isolated contacts that can handle positive, negative and up to 250v DC or AC."
And bring 250VAC into the case of the K3? If a relay is used instead of a solid-state device, it should be located external to the K3 cabinet, especially with 100-250VAC key lines.
The output switching device from the K3 can already switch 200VDC at 5A. For those switching medium-voltage AC/DC amp key lines, or want additional rig-to-amp isolation, a more viable option is to use a solid-state external interface. There are several commercial interfacing products available in both assembled and kit form.
My personal favorite is the "KeyAll" from Jackson Harbor Press. It is optically-isolated from the rig and will switch 500 VAC/VDC at 2.5 A loads.
http://home.att.net/~jacksonharbor/keyall.htm
Paul, W9AC
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