[Elecraft] Key Out jack

[Don Wilhelm]

Pete,

As mentioned by others, the K3(S) KEYOUT jack does not produce any 
voltage - the voltage must be produced by another source (sufficient to 
power the relay).

One method to check the K3 KEYOUT is to use your Ohmmeter.  stick the 
red probe into the center of the jack and the other probe to the shell.
It should read a very high resistance, even infinity (same as your 
ohmmeter reads with the probes attached to nothing) during receive, and 
then go to a very low value (close to zero ohms) during TUNE or Transmit.
If it does not do that, you may have a bad HEXFET driver for the KEYOUT 
line.

73,
Don W3FPR

On 10/13/2017 9:33 AM, N4ZR wrote:
> I am trying to use the Key Out jack on my K3 to key a small relay to 
> protect my SDR from RF.  The 12V at 40 ma is well within the stated rating 
> of the jack, but to my surprise it does not work.  Measuring with an 
> analog multimeter, the jack appears to be shorted all the time, and also 
> to have a very small DC voltage on it.  I don't have a schematic for the 
> radio, so I'm stumped.  Is this a function of the way I'm measuring, or...?
>