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@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...?
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