[ARC5] Keying suggestions

[J. Forster]

I looked at the suggested schematic and it's NOT a good thing IMO. What happens
when the circuit opens is undefined. Yes, it does make sense to isolate the
relays from each other, but there is nothing, other than the reverse breakdown
of the diodes, to prevent huge voltage spikes across the relay coils. That
circuit will cause either the diodes or coils to fail sooner or later.

IMO, you need a snubber across the relay coils, and if you are intent on doing
the diode isolation, you need a snubber across each coil.

-John


Mike Hanz wrote:

> There are *two* ways to employ a spike diode - one *across* the relay
> coil, and the other *in series* with it.  See Steve Williams'
> interesting keying relay experiments on a complete 274N set at
> http://aafradio.org/docs/docs.html , under SCR-274N relay timing notes,
> for a lot of good information.
>
> I'm a little puzzled by the original question, though.  K-53 isn't
> designed well for keying purposes unless you intend to send fairly
> slowly, and keying the MO at the same time isn't conducive to
> stability.  An external relay in the B+ line like the original design is
> actually easier to rig up than the effort needed to modify the
> transmitter wiring, reversible though that might be.  Just a couple of
> data points to think about....
>
> Best 73,
> Mike