KerberosSDR Developments in 2020

Discuss KerberosSDR - 4x Coherent RTL-SDR
rtlsdrblog
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KerberosSDR Developments in 2020

Post by rtlsdrblog » Thu Oct 03, 2019 8:33 am

Thanks for your support with KerberosSDR! The people who've purchased units are helping make this open source code happen.

Posted here is a rough road map of what we're planning for the next stage of KerberosSDR development. Please feel free to post any suggestions for features. We won't be giving a timeframe for these developments, but we are expecting most of them to be completed by the end of 2020.

[*] DAQ Double buffering - We are currently working on revised DAQ code that will allow for arbitrary buffer sizes to be set. The buffer size defines the number of samples the code first collects, then gives to the DSP code to work on. Different buffer sizes may be optimal for different signal types. This is necessary for future developments.

[*] Networked DFing - With several networked KerberosSDR units spread out around a city it will be possible to instantly direction find any signal.

[*] Intermittent Signal DFing Improvements - Right now it is difficult to use DFing with very short intermittent signals. Adjustments to the code will allow us to work on sample chunks that consist of mostly noise.

[*]Passive Radar Blips On a Map (PR + DF) - This will be a combination of the passive radar and direction finding techniques. The idea is that it should be possible to direction find the passive radar blips if we use all 4 on board RTL-SDRs and 4 directional antennas. This would allow us to plot the estimated location (via the distance + bearing) of an object being tracked by passive radar on something like Google Maps. Several improvements to the PR code such as target tracking are required for this to be completed.

[*] DAQ Unit Separation - Processing performance could be significantly improved if the DAQ subsystem and DSP processing code is separated onto two different pieces of computing hardware. Presently if the DSP code is set to run too fast, the DAQ code will lose sample sync due to the CPU + OS on a single device not being able to keep up with the task switching requirements. In the long run it would be better to dedicate a Pi3/4 or other cheap SBC to the DAQ and another computing unit to the DSP. This will allow people to easily read the coherent data stream in other programs too like GNU Radio via an Ethernet network stream. For mobile DFing we will keep the option to use just one SBC.

[*] Android DFing App Bug Fixes + Optimizations - There are a few bugs related to entering out of bounds settings in the app. The app also has room for speed optimization.

[*] Proper confidence values for DFing - Currently confidence is roughly calculated. There exists a potential method for calculating if probabilisticly and this will be tested.

[*] Beamforming - Once the DAQ system upgrades are completed, beamforming and listening to actual signals should be possible. Beamforming will allow you to electrically optimize an antenna array for receiving in one particular direction.

[*] Direct support for two combined KerberosSDR units - Combining two KerberosSDR's gives you 8 antenna inputs. This can improve DFing accuracy, and improve passive radar coverage.

[*] DSP Performance Improvements - There is room for DSP code speed improvements. Ideally we'd like to get passive radar updating significantly faster.

[*] Notching - Calibrating with the antennas connected results in better results, UNLESS there are signals in the spectrum. So calibrating with the antennas can be difficult/impossible in the real world. Adding notches in the DSP may help with this.

[*] Hardware: Switches and an improved calibration PCB - It should be investigated if switches degrade the phase calibration or not. With switches we could eliminate the need to disconnect the antennas when recalibrating.

[*] Improved clutter filters for passive radar - The clutter filter removes passive radar blips from stationary objects. Improved algorithms are faster and result in a cleaner PR display.

[*] A more user friendly UI - Wizards and calculators should be added to make setting up the KerberosSDR settings easier.

ckoval7
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Re: KerberosSDR Developments in 2020

Post by ckoval7 » Wed Oct 09, 2019 7:35 pm

[*] Networked DFing - With several networked KerberosSDR units spread out around a city it will be possible to instantly direction find any signal.
I'm actively working on my own implementation of this. I would love to work together if you're interested.

[*] Hardware: Switches and an improved calibration PCB - It should be investigated if switches degrade the phase calibration or not. With switches we could eliminate the need to disconnect the antennas when recalibrating.

I am presently experimenting with the HSWA2-30DR+ from Mini-Circuits. The PCBs just arrived in the mail today and I will have results by Sunday night. This chip allows selecting between 2 antennas and an internal 50 ohm load.

rtlsdrblog
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Re: KerberosSDR Developments in 2020

Post by rtlsdrblog » Thu Oct 10, 2019 4:31 am

ckoval7 wrote:
Wed Oct 09, 2019 7:35 pm
[*] Networked DFing - With several networked KerberosSDR units spread out around a city it will be possible to instantly direction find any signal.
I'm actively working on my own implementation of this. I would love to work together if you're interested.

[*] Hardware: Switches and an improved calibration PCB - It should be investigated if switches degrade the phase calibration or not. With switches we could eliminate the need to disconnect the antennas when recalibrating.

I am presently experimenting with the HSWA2-30DR+ from Mini-Circuits. The PCBs just arrived in the mail today and I will have results by Sunday night. This chip allows selecting between 2 antennas and an internal 50 ohm load.
Excellent, happy to see contributions! This has been the goal from day one.

For networked operation the stop-gap idea was to get this program compatible with the KerberosSDR http://www.musther.net/RDFMapper/.

But if you're happy to open source and throw your code up on GitHub i'll help test it too.

Will be definitely keen to hear about your switch experiments too. Keep in contact either here on the forums or [email protected].

ckoval7
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Re: KerberosSDR Developments in 2020

Post by ckoval7 » Sun Oct 13, 2019 11:54 pm

rtlsdrblog wrote:
Thu Oct 10, 2019 4:31 am
For networked operation the stop-gap idea was to get this program compatible with the KerberosSDR http://www.musther.net/RDFMapper/.

But if you're happy to open source and throw your code up on GitHub i'll help test it too.

Will be definitely keen to hear about your switch experiments too. Keep in contact either here on the forums or [email protected].
Right now, the networking code is in bits and pieces for testing of various concepts. I'll open up the repo later this year.


I've very pleased with the results from the antenna switch! I've set up the software to run an auto-calibration routine upon changing frequency. Nothing got mangled in the VHF range. I'm not sure how it will translate to the upper UHF range that people seem to use in the demo videos. There's nothing I've cared to DF in the 800MHz range.
Here are some photos: https://photos.app.goo.gl/K1PndvpgotPKdeBU9

Streets814
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Re: KerberosSDR Developments in 2020

Post by Streets814 » Tue Oct 15, 2019 12:52 am

rtlsdrblog wrote:
Thu Oct 10, 2019 4:31 am
ckoval7 wrote:
Wed Oct 09, 2019 7:35 pm
[*] Networked DFing - With several networked KerberosSDR units spread out around a city it will be possible to instantly direction find any signal.
I'm actively working on my own implementation of this. I would love to work together if you're interested.

[*] Hardware: Switches and an improved calibration PCB - It should be investigated if switches degrade the phase calibration or not. With switches we could eliminate the need to disconnect the antennas when recalibrating.

I am presently experimenting with the HSWA2-30DR+ from Mini-Circuits. The PCBs just arrived in the mail today and I will have results by Sunday night. This chip allows selecting between 2 antennas and an internal 50 ohm load.
Excellent, happy to see contributions! This has been the goal from day one.

For networked operation the stop-gap idea was to get this program compatible with the KerberosSDR http://www.musther.net/RDFMapper/.

But if you're happy to open source and throw your code up on GitHub i'll help test it too.

Will be definitely keen to hear about your switch experiments too. Keep in contact either here on the forums or [email protected].
I like this! I purchased a PA8W doppler RDF from wil. Just haven't got around to putting it together as it seams a bit complex. The http://www.musther.net/RDFMapper/ was one of the reasons that sold me on the direction finder.

I am following the KerberosSDR project and will be purchasing some once it evolves a bit more. The rdf mapper, combining 2 devices for accuracy and the ability to network link are big for me.

Keep up the great work!

WA4OSH
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Re: KerberosSDR Developments in 2020

Post by WA4OSH » Thu Nov 07, 2019 9:42 pm

Is it possible to use a GPSDO with the KerberosSDR so that all four (or eight) RTL-SDR DAQs are all sync'ed to the same source?

Eg. the Leo Bodnar Mini Precision GPS Reference Clock
http://www.leobodnar.com/shop/index.php ... &cPath=107

rtlsdrblog
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Re: KerberosSDR Developments in 2020

Post by rtlsdrblog » Fri Nov 08, 2019 3:45 am

WA4OSH wrote:
Thu Nov 07, 2019 9:42 pm
Is it possible to use a GPSDO with the KerberosSDR so that all four (or eight) RTL-SDR DAQs are all sync'ed to the same source?

Eg. the Leo Bodnar Mini Precision GPS Reference Clock
http://www.leobodnar.com/shop/index.php ... &cPath=107
Actually if you can set it to output a 28.8 MHz signal, you could use the clock input on the board and set the MASTER/SLAVE jumper to SLAVE. But i'm not sure what application you have that would require such a precise clock?

k5cg
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Re: KerberosSDR Developments in 2020

Post by k5cg » Thu Nov 14, 2019 3:58 am

I downloaded the V1.5 release today and love it.
- Lockable gain controls are great.
- Antenna spacing entry instead of radius/lambda is great
- Compass is no longer mirror image!

I see there is an experimental 90 degree option (not functional) and I wonder if this was related to my earlier request to be able to setup a square UCA instead of a diamond? If so then the array would need to be set 45 degrees one way or the other, not 90. Choices for -45, 0, +45 would be most versatile.

It would also be great if as many settings as possible could be written to disk and loaded on startup. I hunt for a fox every weekend on the same frequency with exactly the same parameters, so entering the frequency and gain and element spacing could all be eliminated. This would not be required for the IQ parameters because of the calibration steps unless the defaults and last used could be enabled with a checkbox after calibration.

WA4OSH
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Joined: Thu Nov 07, 2019 5:07 pm

Re: KerberosSDR Developments in 2020

Post by WA4OSH » Fri Nov 15, 2019 1:56 pm

WA4OSH wrote: ↑Thu Nov 07, 2019 9:42 pm
Is it possible to use a GPSDO with the KerberosSDR so that all four (or eight) RTL-SDR DAQs are all sync'ed to the same source?

Eg. the Leo Bodnar Mini Precision GPS Reference Clock
http://www.leobodnar.com/shop/index.php ... &cPath=107
Actually if you can set it to output a 28.8 MHz signal, you could use the clock input on the board and set the MASTER/SLAVE jumper to SLAVE. But i'm not sure what application you have that would require such a precise clock?
[*] Stable Frequency tuning
Frequency Stability - We should expect the receiver to stay on frequency and not drift when the temperature changes. To achieve this a TCXO or similar stable oscillator should be used. (Done with optional 28.8 MHz GPSDO)

The appeal of using a GPSDO for a sync source is that it keeps a stable reference, especially in the microwave bands where my interests lie. Frequency drift is a problem for narrow-band signals such as NBFM. single sideband or extremely narrow-band digital modes like JT4, JT9, JT65, QRA64, FT8, PSK31, etc.

(post edited to add clarification)
Last edited by WA4OSH on Sat Nov 16, 2019 2:52 pm, edited 1 time in total.

WA4OSH
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Re: KerberosSDR Developments in 2020

Post by WA4OSH » Fri Nov 15, 2019 2:01 pm

I'm interested in using beamforming and/or MIMO to receive signals from four 3 or 4 element Yagis. I want more than direction finding. I would like to not only know where the main signal is, but also the interferers. The idea would be to click on the signal you want to hear and also to click on the signal you don't want to hear. Then, the resulting stream could be demodulated through something like GRC (GNU Radio Companion) running on yet another RPI?

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