Here is another example of keying an ELECRAFT K3S RIG - by an audio derived CW KEYING circuit - using a software CW KEYBOARD(YPLog in this example) and a Raspberry PI 4 headphone output jack

the Raspberry PI tested to have enough volume output at its own analogue audio output headphone jack - to activate an audio derived CW KEYING circuit - that "grounds" the RIG's CW JACK

- rig used in this video demo is an ELECRAFT K3(S) with qrq+ mode engaged

- software CW Keyboard used in this video demo is YPLog(running via pi-apps WINE setup)

- the CW PITCH that seemed to work best to activate the CW KEYING CIRCUIT was 2400 hertz

The "key" to getting a PI to be able to key the RIG's CW JACK, because of its LOW AUDIO POWER OUTPUT from its headphone jack is picking the "right" audio transformer ratio...8 ohms(pi headphone jack) to 1000 ohms(AUDIO DERIVED CW KEYING CIRCUIT input) etc...

Here is another example of an audio derived CW KEYING CIRCUIT, this time using a diode switch to key the RIG's CW JACK

brief testing of FULL QSK keying of an ELECRAFT K3S at 65 wpm using FLdigi on a Raspberry pi 4, sending 2400hz CW AUDIO out of the PI's headphone jack to an audio derived CW Rig Keying Diode Switch circuit that keys the RIG's CW JACK

the circuit rectifies FLdigi's 2400 hertz CW audio and stores it in a 1uF CAP... and uses that voltage to forward bias a DIODE(for the length of the CW ELEMENT) that is connected across the RIG's CW JACK contacts(orientation of the DIODE is chosen so that the diode by itself, without any bias current, will not allow the RIG's CW JACK to "turn on" and key the rig...) [ diode ~ 1n4007 ]

QSK receive AUDIO is heard between letters at 65 wpm

Here is a LIVE DEMO of an Audio Derived CW Keying Switch Circuit KEYING a RIG's CW JACK

SEUTP: in this demo, FLdigi is sending out a CW KEYING TONE at 1Khz using FLdigi's RT QSK feature/function the input of the SWITCH rectifies and doubles the VOLTAGE from FLdigi's output connected to the switch's input... the circuit stores the voltage doubling in a 1uF cap....when the circuit is receiving 1Khz TONEs from any CW KEYER, FLdigi in this case, the STORAGE CAP's voltage activates the BASE of an NPN Transistor and then the RIG's CW jack being connected to the COLLECTOR of that transistor, the CW JACK gets GROUNDed for every CW ELEMENT...thus keying the RIG's CW JACK