What It Does

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The KX3 Companion in an app that will let the power use of your Elecraft KX3 HF radio easier and lighter. No need for a PC!

It will let you send and receive CW, PSK31 and RTTY by using your mobile phone or tablet keyboard. Optionally you can use an external Bluetooth keyboard connected to your Android device.

You can set up to 10 macros to that can use dynamic symbols to have Call, Name, QTH and Locator automatically updated.

It connects to your KX3 by using the USB Serial cable that comes with the radio. You’ll also need an inexpensive OTG Cable adapter to connect the serial USB to your mobile device. You can find them for a very few dollars. No other cables are needed!

The KX3 Companion app also let you record full QSOs and log them to eventually export them to your favourite QSO logging software and/or service.

With the new SWR Meter functionality you can sweep a frequency range and the app shows you a chart with SWR values. You can select from 3 to 13 steps, each step can be from 5 to 500 kHz. The maximum number of steps depend on the screen size and orientation.

NEW FEATURE: Audio Spectrum and Waterfall!

Selecting the “SPECTRUM” tool, the app shows the audio spectrum. For devices allowing that, you can also attach the KX3 Audio OUT to the device Audio IN for a better signal. The spectrum shows the DSP filter center frequency and its bandwidth. By touching the spectrum you can also see the shift and frequency of every single line. You can zoom in and out to have larger spectrum bandwidth.

Selecting the “WATERFALL” tool, you can see how the spectrum evolved over time. It is very useful feature to spot every signal even the weakest ones!

NOW with touch QSY! To center a signal you simply have to touch the waterfall/spectrum, move your finger to center the signal you want to listen/decode, and release. Now the KX3 is perfectly centered with the new signal and you can start decoding and transmitting.

With KX3 Companion you can:

  • Send and receive CW, PSK31 and RTTY using your Android device keyboard (or even a Bluetooth physical Keyboard)
  • Read and Write messages with room for hundreds of chars (depending on your mobile phone or tablet screen size)
  • XMIT (Chat) Mode – Transmit as you type. Perfect mode to be used with an external Bluetooth keyboard.
  • Switch mode (CW, PSK31, RTTY)
  • Set the frequency and go up/down bands
  • Record and recall up to 10 totally customized macros
  • 4 dynamic symbols for Call, Name, QTH and Locator to be used on macros (you can customize the symbols)
  • Set the CW WPM (Words Per Minute) value with a slider
  • Have up to 10 presets to set power, ATU or whatever you want to program (20 macros on tablet with large enough displays)
  • Customize the serial baudrate, dynamic symbols and date formats to adapt the app to your setup and needs
  • Record and share full QSO logs (everything you send and receive is recorded and saved in a text file)
  • Log your QSO in CSV and ADIF format and send them via email or to any external service supported by your mobile device (log date, time, mode, frequency, call, name, qth and locator)
  • Log received/send RST and received/sent contest serial numbers
  • Audio Spectrum and Waterfall with touch QSY to easy find and center signals!
  • SWR Meter to sweep a frequency range and see the SWR values over that range
  • Compatible with Elecraft K3 as well
  • Support for remote control of the KX3. Instructions here: https://kx3companion.com/kx3remote
  • Support for Piglet (http://pignology.net/piglet) Wifi Serial interface. Instructions here: https://kx3companion.com/piglet

And that is just a start. We are planning more features like ADIF and eQSL.cc support.

Please read the MANUAL to fully understand the potential of KX3Companion.


If you’d like to see some contact us at kx3companion@gmail.com or link to our new forum:



Remember that to connect the Elecraft KX3 to your mobile device you need the serial USB cable coming with the radio and an OTG USB cable adapter. Also make sure that your device is not locked to the use of OTG cables. Some carriers (like Sprint Wireless) may do so. Please check with their customer service.

You can get the app here:


32 thoughts on “What It Does

    • Thanks!

      You’re right and I was thinking about that but then I decided to go with that eventually I can place a little fan on one side and have the air easily flow along the whole length.

      But in most cases rotating 90° would be a step further in performance optimization.

      73, Andrea IU4APC

      • Sorry for not replying sooner. I’m using someone else’s WordPress login and assumed that these comments were for him. If you are going to have the radio standing on the legs, then rotating the heatsinks will facilitate convection (air circulation) between the fins. What I don’t know is whether the improvement will be worth the additional effort. The only way to know for sure is to “measure”. Then again, if your current configuration works you might not want to bother. Oh and I was trying to “picture” in my mind what the rotated configuration might look like, but that’s beyond what my brain is capable of.

        Gary KI4GGX

        P.S. If you visit http://www.unpcbs.com or http://www.ve7fmn.ca you can contact me directly via the webmaster addresses for those two sites.

      • Ciao Gary,

        you were perfectly right and I did it immediately! Thanks a lot. Can’t do a real comparison but it makes perfectly sense what you said and so…

        I tested with WSPR 5W and it works well. Not as good as professional as yours but the important is to see improvement and there are. In reality I’ve seen that MUCH depends on the voltage you apply to the KX3. Working with 9V (that is perfect for 5W) you already have a great improvement simply by using a lower voltage.

        Anyway, I’ll probably post some picture of it later today. Now the KX3 is even more freaky punk!😀

        Thanks again and many compliments for you professional solutions😉 Wish you the best.

        73, Andrea IU4APC

  1. P.S. Make that 90°

  2. Hi Andrea,

    The picture shows you have a audio input/output cable connected from Kx3 to the tablet. Is this necessary for KX3 companion? What is the purpose of having this connection?

    Thank you

    • Hi Chris,
      no it’s not needed for the KX3 Companion to work, but if you want to use the audio waterfall/spectrum you better use it as that way the audio in would be directly connected to the KX3. I suggest you to attach the audio in to the RX I/Q so that you’d be able to see up to 24kHz of spectrum.
      73, Andrea IU4APC

  3. Hi , I would like to know if after all is connected can moving the vfo knob on the radio change the frequency on the pan adapter and can moving the cursor change the frequency on the radio ? thanks John

    • Sure. You can use the physical VFO and the frequency is automatically updated on the app. Or you can set it with the app, and it automatically changes the one on the KX3.

  4. I am having some success on cw using a late model Nexus 7. Not able to get the I/Q audio setup and not sure how to select it over the serial input. Not sure how to continue transmission while manually typing text.

    I am excited about the possibilities of this powerful tool, but have much to learn in order to smoothly operate with it..

    Any guidance is welcomed and appreciated.


    • Hi Rob,

      to have the audio spectrum you should attach the I/Q RX out of the KX3 to the audio in (microphone) port of your Android device. Most of the times it is embedded in the earphone jack. Read here for more details about it: https://kx3companion.com/2014/07/06/mic-headset-splitter-for-smartphones-and-tablets/

      It’s not a real I/Q as the audio in of Android devices is mono. The new Android versions (L) will allow the use of external USB Stereo cards allowing for a full I/Q spectrum.

      If you want to transmit as you type there’s an XMIT mode that can be enabled by long pressing the SEND button. This way it’ll transmit automatically everything you type in the TX field. To come back to SEND mode, long press the XMIT button.

      Let me know if that is what you were asking for🙂

      72/73, Andrea

      • Hey Andrea,

        Have you tried Android (L) as yet? Wondering if I might be able to upgrade the Nexus 7 to (L) or if a new tablet will be required.

        A Happy KX3 Companion user!

      • Ciao Rob,
        yes I’m running Android 5.0 on both my Nexus 5 and 7 2012 and 2013 and everything runs fine.
        So no problem with it.
        Thanks for asking.
        72/73 Andrea IU4APC

      • So have you tried an usb sound card to the I/Q ?
        Curious mind wants to know.

      • Ciao Rob,
        I started testing it but didn’t go too far as I’m pretty busy lately.
        But I’ll surely do more tests in the coming weeks and let you know what I’ll be able to come out with😉
        72/73 Andrea IU4APC

  5. Hi, what is the little keyboard you show in the first photo? Thanks.

  6. Excellent – thank you. 🙂

  7. Andrea, now that Android L is out, will you be able to implement “stereo” I/Q input via USB for better spectrum display? That would be Very cool!

    • Hi Bill,
      yes it’d be cool. Actually I did some initial testing but still have to start the development of the “full” panadapter algorithm. Shouldn’t be difficult but I’m working on so many things lately that actually can’t tell you when I’ll be able to have the full support of the I/Q input.
      I’ll keep you updated.
      72/73 Andrea IU4APC

  8. Andrae, now that Android L is out, will you be able to use stereo USB adapter for spectrum display from I/Q port? That would be Very cool! 73.

  9. Andrae, is it possible to have more than one tablet hooked up to one KX3? Specifically, could I have one tablet running KX3 Companion and a second tablet running KeyApp? How about a third tablet running your panadapter full screen while the first is running terminal mode full screen?

    • Hi Bill,
      No it’s not possible. Maybe using a wireless connection like with the Piglet. I have to try and let you know.
      72/73 Andrea IU4APC

      • How about one tablet connected to the radio, and the second tablet talking to the first via Bluetooth?

      • The bluetooth must be connected to the radio so the problem is on the radio side. You need a single collector able to manage multiple clients. If you use the serial for a USB connection, you can’t use the same serial for Bluetooth adapter😉
        That’s why I’m suggesting the Piglet as actually it can be the only solution allowing multiple clients, but can’t tell you for sure. It has to be tested.

  10. How about using your app with a Microsoft Surface Pro???

  11. I try to use your app with my K3 and Samsung Tablet with Android 5.* . When I try to connect to the K3 a Popup says: An error has occured in sub: java.lang.NumberFormatExeption: Invalid double”” .When continued the app says K3 is connectet but there is no data transfer in either direction. Cable is original K3 and OTG-adapter works fine with camera or HDD etc. Same result with Y-Adapter. Baurate 9600 at both devices, polling 200. What could be the problem?
    Thank you for answer!!

    • Hi Klaus,
      you can try a couple of things.
      First, try setting the baudrate to a higher value like 38400 for both the KX3 and the app. If that doesn’t work then try using 19200 but 9600 is usually too low.
      Second, try uninstalling and reinstalling the app. Sometimes it gets corrupted during the download or use.
      72/73 Andrea IU4APC

      • Hi Andrea,
        now with 38400 baudrate it works fine even with your Key-App at same time open. Sometimes the app hangs after changing things at the trx. Now I´ll have to learn a lot to use all the possibilities! Thank you a lot- 73 Klaus, DL3FAJ!!

      • Great!
        Try slightly increasing the polling time and eventually lowering the baudrate to 19200.
        Enjoy it😉
        72/73 Andrea IU4APC

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