Setting up new Kerberos - feedback and problems

Discuss KerberosSDR - 4x Coherent RTL-SDR
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Setting up new Kerberos - feedback and problems

Post by trollspirit » Sun Mar 01, 2020 2:10 pm


I got my Kerberos in the mail two days ago. First, thanks to all for this great piece of hardware. I’m willing to first try RDF.

I’m having a few issues and couldn’t find answers on the forum after some searches, so here’s my questions.

My setup
- KerberosSDR with 4 x antennas (the small ones, from 400Mhz to 2Ghz)
- good USB cables (GL-inet) and powers sources (one for the KSDR With 2A max, the other for the RPi with 3A max)
- Raspberry Pi 3 with 7in touchscreen + RiiX8 for mouse/keyboard
- Smartphone Dogee S80 lite with android 8.1.0 Kernel 4.4.95

Problem 1
The Kerberos and the RPi are working well. For some obscure reason I got the android hotspot to work once, then the RPi would not connect and fall back to it’s own KerberosPi wifi network. Not very handy but not a big problem, I’ll try to fix that later. I usually start the android first, then the Kerberos, then the Rpi.

Problem 2
On the Rpi screen I can see the Kerberos program interface, but the graphs are not updating, and due to some weird resize bug, I cannot see the whole graphs (only the top ones, impossible to scroll down to the others)

On the Android terminal, I have no issues on connecting to KerberosPi network, and the setting the frequency and gain. I have nice Spectrum graphs, that update every second or so, and an update rate between 250ms and 400ms.

Problem 3
Then when I switch to Sync, I can check both boxes “Enable Sync Display” and “Noise Source ON/OFF”. However, I cannot get any graph to appear at first. If I click on “update”, the “Noise source” checkbox un checks, and nothing happens. I finally got the graphs after some time (More than 10 minutes). Sample Sync and Calibration of IQ went well. I got a sample rate of 3.5s at that time (is it normal?).

Problem 4
Went on to fix BW, FIR and decimation (no problem), then to DOA, and again the graph took a long time to appear (more than 10 minutes again).

Questions :
- I suppose my Rpi3 is not fast enough to handle the load, am I correct? Should I switch to Rpi4?
- I am going to mount all this in my car, a few questions for those who already did it :
. What’s the best option for power supply? Plug in directly in fuse box, but what converter to use to go from 12V to 5V?
. Is the paint on the car body an obstacle to a good ground plane for the 4 magnetic antennas?
. Due to the fact that the antenna array is changing with the tracked frequency (s’ changing), as anyone developed an adjustable antenna array, and if yes, how?

Thank you all, I will come back soon with my first results...

Good hunt,

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Re: Setting up new Kerberos - feedback and problems

Post by rtlsdrblog » Mon Mar 02, 2020 1:43 am

Problem 1

Not sure why it's suddenly not connecting, double check the WiFi name and password

Problem 2

The resolution of your screen is probably far too low to accommodate the GUI. I'd suggest using the web interface or getting a better screen if that's a problem.

Problem 3/4
The Pi 3 is fast enough to run the software, but 3.5s is too slow so something seems wrong.

Is there something else running in the background? Did you ensure that the FIR is set to 0, and the decimation is set to 4? Did you double check that the other screen's graphs like the spectrum display, DOA, and passive radar displays are disabled before calibrating?

Or is your Pi 3 overheating and thermally throttling?

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Re: Setting up new Kerberos - feedback and problems

Post by KD7CAO » Sun Mar 29, 2020 3:14 am

I am experiencing similar issues with a Rpi4 4GB. Been trying to get the calibration tests completed but the graphs continue to show a static display. Haven't tried just connecting to my Arrow Array yet, but also noticed another small problem. The Pi will not load if the KSDR is receiving power from an external source. If you boot the Pi and let it power the KSDR it will at least load and get the test from CLI.

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