KerberosSDR Interface to Gnu Radio Companion (GRC)

Discuss KerberosSDR - 4x Coherent RTL-SDR
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WA4OSH
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KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by WA4OSH » Thu Nov 21, 2019 7:21 pm

Could someone tell me more about the Interface between the KereberosSDR and the Raspberry Pi that's running GNU Radio Companion? Since the RTL-SDR source block works with only one RTL-SDR, is there a block that selects one of the four RTL-SDRs, or a block that has four outputs? Are there additional blocks needed to control the KerebrosSDR such as turning on and off the noise source, etc.

Image

--Konrad, WA4OSH

WA4OSH
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by WA4OSH » Thu Nov 21, 2019 9:46 pm

I have found this python code that might give a clue how the KerberosSDR streams are packed over the USB interface:
https://github.com/rtlsdrblog/kerbeross ... eceiver.py

--Konrad, WA4OSH

WA4OSH
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by WA4OSH » Fri Nov 22, 2019 7:28 pm

This GitHub entry Multi-RTL presents a two-channel Phase Coherent Receiver based on two RTL-SDR dongles.

Multi-RTL is a GNU Radio block that transforms cheap multiple RTL-SDR receivers into multi-channel receiver.

Multi-RTL is the first software solution that enables synchronous reception with each channel based on a RTL-SDR receiver tuned to a different central frequency. The synchronization is done automatically and in software - without the need for any additional electronical hardware.

https://github.com/ptrkrysik/multi-rtl

Could this be adapted to KerebrosSDR, a four-channel phase coherent receiver??

--Konrad, WA4OSH

rtlsdrblog
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by rtlsdrblog » Mon Nov 25, 2019 9:34 am

WA4OSH wrote:
Fri Nov 22, 2019 7:28 pm
This GitHub entry Multi-RTL presents a two-channel Phase Coherent Receiver based on two RTL-SDR dongles.

Multi-RTL is a GNU Radio block that transforms cheap multiple RTL-SDR receivers into multi-channel receiver.

Multi-RTL is the first software solution that enables synchronous reception with each channel based on a RTL-SDR receiver tuned to a different central frequency. The synchronization is done automatically and in software - without the need for any additional electronical hardware.

https://github.com/ptrkrysik/multi-rtl

Could this be adapted to KerebrosSDR, a four-channel phase coherent receiver??

--Konrad, WA4OSH
Yes it sure could. Probably actually needs no modifications, just turn off two RTL-SDRs on the DIP switch.

I believe Multi-RTL makes use of external signals for synchronization though, so not as versatile as using the KSDR software with noise source.

WA4OSH
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by WA4OSH » Fri Nov 29, 2019 4:17 pm

The current Raspberry Pi and web and Android application are nice, but they lock-in the KerberosSDR into doing two things: Direction Finding and Passive Radar. There's far more that can be done with what's here, but it needs to be opened-up so that other things can be studied with it.

I would actually would like understand the USB interface to the KerebrosSDR so that I can do more things with it, especially use it for other applications.

How about an ADS-B receiver that can also listen to the local airport frequencies at the same time? I want to hear the audio.

How about a weather channel radio that can listen to the four strongest signals at once? I want to hear the audio.

How about an emergency beacon radio that can listen on 121.5, 243, and 406 MHz at the same time? I want to hear the audio.

The current Raspberry Pi and Android applications don't allow access to the audio.

--Konrad, WA4OSH

ckoval7
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by ckoval7 » Sat Nov 30, 2019 4:20 am

The Kerberos SDR is literally 4 RTL-SDRs on one board with their clocks tied together. They can be treated as 4 separate RTLs in any SDR program.

WA4OSH
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by WA4OSH » Wed Dec 04, 2019 9:47 pm

So the four Rafael Micro R820T2 (24 - 1766 MHz) RTL-SDRs are tied together with a USB Hub. So you would use four RTL-SDR source blocks? How do you select them in the source block?

--Konrad, WA4OSH

ckoval7
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by ckoval7 » Wed Dec 04, 2019 11:35 pm

WA4OSH wrote:
Wed Dec 04, 2019 9:47 pm
So the four Rafael Micro R820T2 (24 - 1766 MHz) RTL-SDRs are tied together with a USB Hub. So you would use four RTL-SDR source blocks? How do you select them in the source block?

--Konrad, WA4OSH
I never really use the RTL-SDR source blocks in GRC since I prefer gr-osmosdr. You'd select them by device index or serial number. Device string would be something like "rtl=0" for the first one or "rtl=3" for the last one. You can replace the single digit with the serial number of the specific rtl to guarantee you're picking the right radio since the device index might not necessarily line up with the arrangement on the PCB.

rtlsdrblog
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Re: KerberosSDR Interface to Gnu Radio Companion (GRC)

Post by rtlsdrblog » Sat Dec 07, 2019 1:03 am

WA4OSH wrote:
Fri Nov 29, 2019 4:17 pm
The current Raspberry Pi and web and Android application are nice, but they lock-in the KerberosSDR into doing two things: Direction Finding and Passive Radar. There's far more that can be done with what's here, but it needs to be opened-up so that other things can be studied with it.

I would actually would like understand the USB interface to the KerebrosSDR so that I can do more things with it, especially use it for other applications.

How about an ADS-B receiver that can also listen to the local airport frequencies at the same time? I want to hear the audio.

How about a weather channel radio that can listen to the four strongest signals at once? I want to hear the audio.

How about an emergency beacon radio that can listen on 121.5, 243, and 406 MHz at the same time? I want to hear the audio.

The current Raspberry Pi and Android applications don't allow access to the audio.

--Konrad, WA4OSH
If you just want to do those things, then you can simply use any other RTL-SDR compatible software that is out there now. The KerberosSDR is at it's core just 4 RTL-SDRs, and it shows up that way when you plug it in. It's exactly the same as if you plugged 4 dongles into the PC.

KerberosSDR is only different to 4 individual dongles when it comes to applications that require coherency, like passive radar and direction finding. The additional hardware in the KerberosSDR like the noise source, cal board, single clock source, and other minor changes are what make coherency possible. As there is not much software for coherent applications out already, we made our own for the project so that we can show off the coherent capabilities.

I think what you're actually asking for is an Android app that will easily allow you to access audio streams from the 4 dongles? We could look at doing something like that if people are interested. We could make use of existing DSP toolchains like csdr. I think even just a web interface would work for listening to an audio stream as that would be device agnositc.

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