[Elecraft] K3 TX light flashing when RTS=PTT

[Geert Jan de Groot]

>> At Field Day this year, the K3 TX light started flashing when we loaded
>> N1MM to use RTS=PTT to send .wav files.  This only occurs when RTS=PTT is
>> set on the rig.   I thought it was a bug in N1MM but it also does this 
>> when
>> using N3FLP's logger and the flashing corresponds to the polling rate
>> (which N3FJP allows one to set).
> 
> Check whether RTS is active when you powered up the K3. Yaesu radios 
> have a similar safety feature (cannot transmit if key is engaged during 
> powerup, it avoids the radio immediately transmitting when the 
> microphone is jammed under some electronics project or the cat sleeps on 
> top of the morse key.

I apologise for replying to my own mail but the exact behavior is 
described in the K3S manual (page 20):

PTT and Keying (via DTR and RTS)
In the K3S, these are not used as serial I/O handshaking lines. Instead, 
the K3S can use these as PTT IN or KEY IN (see CONFIG:PTT-KEY). The 
default for both signals is inactive. Refer to application software 
documentation to determine if it can use RS232 signal lines for PTT or 
keying.

Use these signals with caution. A computer may assert DTR or RTS during 
power-up, causing the K3S to transmit unexpectedly. If a computer or 
other device asserts RTS or DTR while you’re using the PTT-KEY menu 
entry, the K3S will enter TEST mode as a precaution, allowing you to 
change the menu setting if required.


... and test mode shows as the TX light flashing.

So it's even in the manual!

Geert Jan