CW with SDR transmitters such as Pluto and LimeSDR using SDR Console (Windows)

  • Hello all,

    I tried to find a way to transmit CW using a LimeSDR Mini and SDR Console. Until now I used an external tone generator (600 Hz), keyed externally with my electronic keyer (ETM-9COG).

    After searching the internet for a while I found tool called "Morse Keyer 4.3". This software makes use of a serial interface (RS232 or USB to TTL converter) as a keyer input and produces an adjustable tone that can be put on any of the installed (real or virtual) sound devices of your computer. I use the software with Windows 10.

    The tone frequency can be adjusted, as well as the softness rise/fall time, to avoid clicks (see screenshot).

    Resources and download:…rse%20Code%20Tools%204.3/

    I connected my electronic keyer output directly to the pins marked "Manual Key", see picture (source: MorsePower Website).

    For SDR Console, I use the SSB function with VOX enabled and the Virtual Audio Cable (B) as input.

    Have fun, see you on CW!

    Vy 73

    Holger 'Geri', DK8KW

  • If you disconnect the red 5V line and connect the wire to Pin 9 of the PL2303 chip, then you can use the paddle function also. The red line (DSR) will then be the left paddle and the blue Line (CTS) the right paddle.

    If you want to use the software for keying a normal transceiver, you can use the yellow line (RTS) to do this. The yellow line act as an output for the CW signal. But you should add a transistor to do the CW keying.

  • Hi Geri,

    Thanks so much for posting this! a great solution for those of us working with a SDR in tx.

    I tested it on two computers, the first with a native serial RS232 hardware com port and it works fine. However in a newer PC with no RS232 port and using a USB to COM converter the time latency is high and cannot key faster than 5 wpm with a straight key.

    In any case a great solution!

  • Hi Holger,

    thanks a lot for this hint which is really helpful. So far, I have also been using a keyer with a built-in tone generator (Ultra PicoKeyer by N0XAS) to transmit CW audio in SSB mode. With a good and narrow TX filter, this worked quite well in SDR Console.

    The solution you suggested works much better for me. However, I had a hard time getting it to work. I soldered the cable for the serial port (luckily, my laptop still has a native COM1 port), and it worked at first try with a hand key. But that was not what I wanted. So I started playing around with different keyers I had in the shack. The PicoKeyer would not key the COM port at all, my K1EL WinKeyer sort of worked, but not very reliably. So the serial connection seems to be somewhat sensitive. Then I tried my Palm Radio Code Cube (which they unfortunately do not build any longer). This one worked right out of the box. I suppose the other keyers require an additional driver stage or even a relay.

    The combination of Morse Keyer 4.3 and SDR Console really produces a very nice and clean CW signal, even without additional filtering!

    73 and CUL in CW!

    Felix, DL5XL.

  • Oh wow, what did I do!???

    When you download the "Morse Keyer 4.3" package there is another program called "Morse News 4.3". I guess this is to practice CW -- a very useful feature, I think. But somone (I assume accidently?) started that program and now we have the latest news on .530!

    Please check your station if that is accidently you who transmits the news automatically.

    Best 73

    Holger 'Geri', DK8KW

  • it was me ... just to show HOW CLEAN AND NARROW such a signal from the keyer software is (the news reader has the same setable rise and fall time settings as the "normal keyer" ... a bit longer rise time ... and signal is VERY narrow)

    its a nice tool to spread out news (or other urgent messages) ...



    i wanted to show how narrow (no keyklicks!!) such a signal can sound over the air ... much better as switching on sdr console to tx (permanent on with tone !!!)) and key the amp on and off to send cw signs

    yes i have seen and heard such signals on qo100 ... UGGLYYY WIDE SPLATTER

    it was just to show a superb cw quality (remember it was just to SHOW IT IN LIVE)

    so at least we know it works fine (and i switched the news reader off for now)

    the keyer soft produces a superb cw signal quality ... and thats all i wanted to show with the newsreader ...

    greetz sigi DG9BFC

    best 73 and cu on the bird :)

  • How do you guys actually use this software?

    I briefly tried it and deleted it again because the latency was making the software absolutely unusable for me...

    When I was using it straight on my PC (= hardly any latency) it was usable to locally generate CW in my headphone or loudspeaker.

    Even around 20WPM iambic paddle mode with the mouse mode worked very well for me with nice sounding CW.

    But as soon as I switch the output to virtual audio cable to feed into SDR-Console for TX, the delay via the satellite makes it unusebale.

    I therefore tried to activate the local echo output on my standard soundcard in the virtual audio cable settings for monitoring my CW locally, but even that had a terrible latency and unclean output of the monitor signal.

    It would be actually great if it would heve two selectable outputs - one into a VAC for TX and one to the local soundcard (the latter with very low latency)...

    73, Oscar

  • DJ0MY

    Hello Oscar,

    >How do you guys actually use this software?

    I use an external electronic keyer (ETM-9COG) with a Bencher paddle and I listen to the sidetone of that external keyer while keying. Volume of the received signal is attenuated while transmitting, so I don’t get distracted by the latency.

    So, I just make use of the software‘s ability to produce a soft keyed clean tone an I don’t use the electronic keyer part of it.

    Best 73, stay safe!

    Holger ‚Geri‘, DK8KW

  • As a newbee to QO 100 I am also looking for a CW solution. In my CW courses I used the Morserino 32 to work with Mumble and Zoom for CW over Internet - the Morserino has a special sine output with a very clean CW signal - maybe this is a solution to feed it to SDR Console without delays. Will give it a try when my components are all together.

    vy 73 Thomas DG6UAX

  • I have now tested several variants. Almost everything was unusable. The delay is too long. Both via a sound card input and via USB. Because you need an undelayed audible tone in order to give cleanly. And that only works if the morse keyer generates it directly. If this sidetone is generated on the PC, the delay is too long.

  • Hi all,

    the topic is old - anyway - is there a solution for it ?

    I came across the same issues all mentioned above when looking for the answer how to become QRV in CW on QO100 (and I'm still not).

    I have a brand new station with Pluto RevD, external clock 40 MHz stabilized by GPSDO, same for LNB but 25 MHz, SG-Labs Pre-amp and PA, Teufel Headset, SDR-Console, 85 cm dish, homemade PotyFeed.

    Station is running fine in SSB but I'm a bit disappointed because it seems to be difficult to operate in CW. I would like to use headphones for RX and I would like to hear the CW tone without any latency when making CW in the same headphones where I hear the downlink signal.

    I have a FT232 USB module connected, CTS as key input line for MorseKeyer 4.3, virtual audio cable to SDR-Console - all fine. But when I try to hear my tone using the monitor function of SDR-Console, the latency issue comes up. No CW keying possible with that.

    Is there any idea how to improve the situation (in the meantime) ? Sorry when I did not found an existing answer during my search - I've tried my best but was not successful.



  • Here is a video that explain how to make it using a real cw keyer.

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    73 ed py2rn

  • Hallo Nick,

    diese Lösung hatte ich auch schon gefunden. Sicher nicht schlecht, aber halt einige Spezial-Bauteile, Controller, Display usw. Da ich gern Analogschaltungen baue, habe ich eine eigene Schaltung entworfen. Diese soll über Line-In/Line-Out an die Soundkarte des PC's angeschlossen werden. CW-Ton wird per OPV als Sinus erzeugt, Frequenz variabel. Tastung am Ausgang via J-FET. Kopfhörer/Lautsprecher-Verstärker ganz einfach mit LM386 mit Mischer-Poti am Eingang, so dass man die RX-NF und den CW-Mithörton nach belieben mischen kann. TX/RX Umschaltung über die VOX in der SDR-Console. Das Teil hat nur keinen eigenen Keyer, den muss man also von außen noch anstecken, wenn man Squeezen will. Für Handtaste oder Bug würde es auch so gehen.

    Gefällt mir trotzdem besser, als das herumprobieren mit irgendwelcher Keyer-Software auf dem PC, für die es evt. keinen Support gibt plus Latenz durch USB-Adapter plus Latenz durch VAC software + Kosten für VAC Software usw. usf.

    @Ed as I did similar tests with the MorseKeyer software + VAC I have doubts that the latency between the squeeze keyer input and the CW audio is short enough for me. Can you provide the delay in ms between pressing the squeeze paddle until the CW tone is audible for you? Especially in the case, when FT232 module is used for USB connection. My PC has no classic serial port anymore.