What circuit for computer audio out to key rig?

I recall W4BQF mentioning on his site somewhere that QRQ folks use sound card output to key their rigs. I'm wondering what circuit you guys use? Is the audio out just normal "sidetone" output?


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Here is a video demo of testing these kind of circuits to key CW on a RIG to find the "best" audio pitch & volume

AUDIO DERIVED CW KEYING CIRCUIT - (what audio frequency to use)

Finding the "best" audio pitch to generate the most voltage from this passive circuit - sent to this circuit from a software CW Keyer's audio PC sound card output

2k load on the TRANSISTOR that grounds the RIG's CW JACK...
when it is turned 'on' by the audio at the circuits input stage.


finding the "best" amount of volume ...
too much = ~ heavier keying
too little = ~ lighter keying

the green wave is the cw keyboards output wave, the RED WAVE is what is being transmitted by the rig from being keyed by the audio derived cw keying circuit shown in the webcam view above on the breadboard...there is an 8ohm to 200 @ ohm isolation transformer at the input yellow with the green clip leads etc... the AD5DZ CW KEYBOARD also has an adjustment for compensation you can increase or decrease the length of the cw elements so between the two settings of volume and compensation...you can dial in how heavy or light you want the rig to sound

Here is a LIVE DEMO of using the full wave doubler circuit with a MOUSER 8 ohm to 200 ohm input transformer - this is a REMOTE CW setup, where a Low Power AM transmitter(1630 Khz) is modulated at the remote OP's desktop by the audio output of a CW KEYBOARD, and an AM RADIO RECEIVER's audio output headphone jack by the RIG is used to FEED the AUDIO DERIVED CW keying circuit input, keyed at 50 wpm

using a low power AM transmitter circuit to modulate with CW AUDIO from a CW KEYBOARD...transmitting at 1630 Khz, to a "rig side" AM RADIO Receiver(GE SUPERRADIO II)...where the AM RADIO's audio output is connected to an AUDIO DERIVED CW Keying Circuit's input

- this video demo's remotely keying CW on an Elecraft K3S at 50 wpm


 Here is another interesting low cost circuit that might work well for an audio derived CW RIG Keying circuit:

FROM:  https://web.eecs.umich.edu/~prabal/pubs/papers/kuo10hijack-islped.pdf

take a look here too...i think the FETs used in this article are no longer being made...  however, there may be some help here -



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


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