KerberosSDR Running RF Direction Finding on a Tinkerboard

KerberosSDR (formerly HydraSDR) is our upcoming 4-input coherent RTL-SDR. It's designed for coherent applications like RF direction finding, passive radar, beam forming and more, but can also be used as a standard 4-channel SDR for monitoring multiple frequencies. In this post we demonstrate the direction finding application running on the TinkerBoard. 

Reminder: If you have any interest in KerberosSDR, please sign up to our KerberosSDR mailing list. Subscribers to this list will be the first to know when KerberosSDR goes on preorder, and the first 100 sales will receive a discounted price.

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KerberosSDR Updates

This week we've managed to get the KerberosSDR demo software made by Tamás Peto functioning on a TinkerBoard. The TinkerBoard is a US$60 single board computer. It's similar to a Raspberry Pi 3, but more powerful. We've also tested the app running on the Raspberry Pi 3 and Odroid XU4. The Pi 3 is capable of running the software but it is a little slow, and the Odroid XU4 is a little faster than the TinkerBoard. In the future we hope to further optimize the code so even Raspberry Pi 3's will be smooth.

In the video below we used a circular array of four whip antennas connected to KerberosSDR. The TinkerBoard is connected to KerberosSDR and is set up to generate a WiFi hotspot, which we connect to with an Android phone and a Windows laptop. The Windows laptop connects to the TinkerBoard's desktop via VNC, and the Android phone receives an HTML/JavaScript based compass display via an Apache server running on the Tinkerboard. With this setup we can wirelessly control and view information from KerberosSDR and the TinkerBoard.

We've also tested the KerberosSDR system on a real signal, and have found it to work as expected. More demo's of that coming later.

For more info on KerberosSDR please see our previous announcement post.

KerberosSDR Direction Finding Test 2: Tinkerboard + Circular Array

KerberosSDR Prototype
KerberosSDR Prototype with TinkerBoard Running Computations


  1. Damon

    I bought 2 KerberosSDR’s and I bought a Tinkerboard S and a Raspberry PI 3+ to use each with.
    I was going to connect them with a short USB to MicroUSB cable, but then I noticed that the Tiker board and Pi will ‘fit’ directly onto the KerberosSDR’s board via the 40-pin header bar. When you remove the enclosure bottom there’s even instructions on the board next to the 40-pin header bar that say:
    “Please remove JP2 jumper for Raspberry Pi operation”
    “Power booth KerberosSDR and RPi fromUSB PWR.”

    Will this work with both the Pi and the Tinkerboard?
    What are the drawbacks?

  2. John Scherer

    While maybe not quite as fun as passive radar, would it be a fair assumption that this might also work with trunk scanning apps like unitracker?

    • Timmy

      If you look at the image of the PCB above there are four metal shields, under each one of those cans is a R820T2 tuner and, outside and below are four RTL2832u USB 2.0 interface chips (which provide the ADC). That is basically the guts of four RTL-SDR devices. There are other parts like four LDO voltage regulators, a Zener diode avalanche white noise generator that can be switched in as a signal source for synchronisation, and a four port USB hub.

      So anyhow at the end of the day the KerberosSDR can be treated exactly like four standard RTL-SDR sticks, with a nice clean power from four individual Low Drop Out linear regulators.

      I do not see any reason at all why a single KerberosSDR can not offer excellent performance for trunk scanning apps like unitracker if treated as one, two, three or four individual RTL-SDR devices. But the photo is not clear enough photo to tell if there is a Bias-T, on any port, I suspect that there is not because the power budget is already pretty tight, but it depends on how the device is powered and how many GPIO pins are spare, but my gut feeling is that there is no Bias-T, which is not a big deal, but I could be wrong.

      • LamaBleu

        Hi Timmy.
        Yes 4 SDR’s on one board but using the same USB port to communicate with host computer ?
        Watching the picture, even searching and google, I’m not 100% sure to understand. Looks like a SDRx from outernet with 4 tuners.
        I think the USB ports shown are from a TinkerBoard connected to the KerberosSDR acting as a hat ??

        • Timmy

          There is an onboard 4 port USB hub chip.

          Similar, but with a common clock shared between all tuners and the RTL2832u (ADC->USB)

          I agree with that the 4 USB ports and the Ethernet port on the left hand side of the image is from the TinkerBoard, I’m about 99.99% sure that it is not a hat board. At the bottom of the board near the middle is a micro-USB cable.leaving the KerberosSDR it goes out of frame and is plugged into the TinkerBoard (bottom left of the image).

          • admin

            Yep the left is the TinkerBoard, connected to a Rpi compatible header under the KerberosSDR board. The GPIO headers don’t have USB, so USB still needs to be provided to it via a USB cable.

        • admin

          Outernet (now “Othernet”) developed the board, so no surprises that it is similar to SDRx 🙂 The left is indeed the TinkerBoard. It doesn’t need to be there if you want to use it with a PC/laptop.

    • admin

      Yep it would work fine with Unitrunker. If you’re not interested in coherent applications, you can still use it as a bank of 4 separate RTL-SDRs that you can use for any RTL-SDR related project. The main feature vs 4 separate dongles, is that the KerberosSDR RTL-SDR units are locked to the same clock, so coherent applications are possible.

      The onboard USB hub allows you to plug the board into only one USB port on your PC/SBC rather than using up four separate ports. If you’re PC/SBC can’t provide enough power via one USB link, there’s a second microUSB port for power.

  3. Timmy

    Is there a separate power supply for the board ? Or is it using two USB ports (one for power with data and second one for extra power alone).
    A RTL-SDR would typical be about 260 – 300 mA @ 5 volts (1.3 to 1.5 watts).
    And a single USB 2.0 port is designed to supply at most 500mA @ 5 volts (2.5 watts)

    I know that some of the power budget will gained back by having only one TCXO, but there will also be some spent on the internal 4 port USB hub chip.

    • admin

      There are two microUSB ports, one for pwr+data and one for pwr only. If your PC/SBC USB port is modern, it can provide up to 1.5-2A, so possible to run the four from one port. But if you’re using an older port that can only give 500mA, you can use the extra pwr only microUSB port with a separate power supply, or second connection.

      In the video the KerberosSDR is connected to a typical 3A power supply (like what you get with a Raspberry Pi3), and the Tinkerboard connects to it via USB and gets power from the USB and a Rpi compatible header on the back.

  4. LamaBleu

    Hi just curious, regarding software, is this nice board compatible with RTLSDR world ? Can we consider it’s 4 RTL devices on the same board ? I mean similar to outernet SDRx boards with 4 addressable devices? tks

  5. Max

    Did you register the domain before releasing the name this time?
    According to my internet provider it is blocked because contains malware.

  6. JTC

    Very interested in this project. Any word yet on what the price of the KerberosSDR will be? Rumor mill is saying somewhere in the neighborhood of $100~$200 USD? Will there be purchase options that include a Raspberry PI or ODroid, etc…

    • admin

      Yep likely to be in that price range. We won’t be including single board computers with it. It’s easy enough to obtain those yourself cheaply (or many already have some lying around).

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