[Elecraft] Collins 30L-1 amp with the K3

[Eric Swartz WA6HHQ - Elecraft]

HiButch,

Do not hook the K3 directly to the 30L-1. The K3 only switches positive 
voltages to ground on TX. Hooking up a negative voltage will not work 
and may damage the Keyout keying transistor.

An external relay or a negative voltage keying transistor buffer are the 
best ways to do this.

Butch Schartau wrote:
> I want to use a Collins 30L-1 amp with my K3, when I plug the 30L-1 amp
> control cable into the K3 KEY OUT jack, the 30L-1 keys.  The 30L-1 is keyed
> by grounding it's key line (pulling -160 DC to ground).  The K3 specs says
> +200 VDC, at 5 amps, I guess the K3 does not like the minus voltage on the
> 30L-1 key line, any suggestion other than an external relay?
>
> Butch K0BS
>