[Elecraft] Continuing saga with Tx Inhibit and the KX3 - possible firmware bug?

[Chris Cox, N0UK]

Having solved the need for getting +Ve Tx Inhibit working on my KX3/10GHz Transverter integration using a mosfet switch to invert the signal and configured the KX3 for 0v Tx Inhibit, I had opportunity to test it out this afternoon.

The solution seemed to work fine on SSB but I now have a weird issue when using the rig on CW.

If I manually select transmit with the microphone PTT and then wait for the transverter sequencing to remove Tx Inhibit and then key CW with the paddles, the system works as desired.

If I key the system using VOX, the Tx Inhibit functions correctly, fully disabling the transmitter from producing RF until TxInhibit is removed BUT the CW sidetone becomes permanently on from the moment TXInh disappears regardless of whether I am sending or not.  It stays present until I press any of the buttons on the KX3.   This happens regardless of which band is enabled, but occurs whenever TxInhibit is present.

If I remove the TXInh fro the GPIO input (but leave the option enabled in the KX3 config) the rig operates normally.

Can anyone else replicate this oddball behavior?  It seems to be a firmware bug.  I have tried removing power but that does not alter the effect.

Again, all works just fine if I don’t try to key the paddles before PTT sequencing has changed over.

Chris Cox, N0UK
chrisc at chris.org