Hello Dwight,
The External PA Key jack does not source current to drive a relay;
rather, it sinks current from the relay, so you essentially connect your
relay between the +12 volt source and the External PA Key jack. So, if
what you're asking, is how to connect an external relay with a 12 volt
coil to the External PA Key jack on the KPA100, then...
- If you're using a 12 volt power supply separate from the one powering
either your K2 or or KPA100, be sure that the external power supply
ground is also connected to the KPA100 ground.
- Connect one lead of your relay to the (+) lead of your 12 volt supply
through an in-line fuse holder, containing a 1/2 amp or 1 amp fuse.
- Connect the other lead of your relay to the External PA Key jack
center pin on the KPA100.
- I'd recommend that you also place a diode such as a 1N4001 across the
relay coil to suppress inverse EMF when the relay is de-engergized. This
diode should be connected such that the cathode end of the diode (end
with the band on it) is connected to the relay coil connection which
goes to the (+) positive 12 volt line via the fuseholder, and the anode
end of the diode (end *without* the band) should be connected to the
end of the coil which you connected to the KPA100 External PA Key jack.
(Do NOT reverse the connection of this diode; Q9 in the KPA100 will not
be appreciative, although your in-line fuse will protect it)
That should do it. When you transmit, your external relay will be
energized, and you should be able to key your heathkit amplifier via the
relay contacts.
73, Dale WA8SRA
Dwight wrote:
>So, having tried and not succeeded, does anyone have a circuit suggestion to
>tie in with the External PA Key jack on the kpa100? I need for it to key a
>12 volt relay, so I can use it with my heathkit. Some how, Im missing it....
>
>
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