Feature requests / development ideas

Discuss KerberosSDR - 4x Coherent RTL-SDR
k5cg
Posts: 13
Joined: Thu Aug 15, 2019 8:52 pm

Feature requests / development ideas

Post by k5cg » Fri Aug 23, 2019 4:19 am

1. The radius of 4 antennas on the roof in the North/East/West/South arrangement of my car barely fits across the roof (specifically the East to West dimension). Would it be possible to have an option that would allow the array to be rotated 45 degrees so the antennas can be placed in a NW, NE SE, SW (square rather than diamond) pattern? It would fit a square car roof better and provide a larger ground plane for all antennas when using lower frequencies (2m).

2. Considering most people are going to use 4 identical antennas, would it be possible to have the gain controls linkable so they can optionally be locked together and controlled by a single selector control?

3. A button in software to gracefully shutdown the Pi. I always worry about pulling power.

Thanks

GermanTerrible
Posts: 13
Joined: Wed Nov 21, 2018 10:00 am

Re: Feature requests / development ideas

Post by GermanTerrible » Sun Aug 25, 2019 2:52 pm

I have another idea. Could the antenna array be used as a virtual single directive antenna, with no rotator? If possible, would it neccesarily be vertically polarised, or could be horizontally as well?

Thank you.

rtlsdrblog
Site Admin
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Joined: Mon Nov 19, 2012 11:54 pm

Re: Feature requests / development ideas

Post by rtlsdrblog » Mon Aug 26, 2019 4:37 am

k5cg wrote:
Fri Aug 23, 2019 4:19 am
1. The radius of 4 antennas on the roof in the North/East/West/South arrangement of my car barely fits across the roof (specifically the East to West dimension). Would it be possible to have an option that would allow the array to be rotated 45 degrees so the antennas can be placed in a NW, NE SE, SW (square rather than diamond) pattern? It would fit a square car roof better and provide a larger ground plane for all antennas when using lower frequencies (2m).

2. Considering most people are going to use 4 identical antennas, would it be possible to have the gain controls linkable so they can optionally be locked together and controlled by a single selector control?

3. A button in software to gracefully shutdown the Pi. I always worry about pulling power.

Thanks
Thanks for the suggestions. We'll look at adding those suggestions in the next update.

rtlsdrblog
Site Admin
Posts: 2428
Joined: Mon Nov 19, 2012 11:54 pm

Re: Feature requests / development ideas

Post by rtlsdrblog » Mon Aug 26, 2019 4:39 am

GermanTerrible wrote:
Sun Aug 25, 2019 2:52 pm
I have another idea. Could the antenna array be used as a virtual single directive antenna, with no rotator? If possible, would it neccesarily be vertically polarised, or could be horizontally as well?

Thank you.
Do you mean for beam forming? It's possible but at the moment the code doesn't allow for the full IQ data to be processed, so it requires some modifications to be used for demodulation etc.

k5cg
Posts: 13
Joined: Thu Aug 15, 2019 8:52 pm

Re: Feature requests / development ideas

Post by k5cg » Sun Sep 01, 2019 2:02 am

More ideas... yes, sorry. After using for a while... so.

1. A way to listen to audio from one of the RTLs (select one or just #1 only) by either a jack on the side of the KerberosSDR housing or from the Pi Audio jack or maybe Bluetooth (to an earpiece or car).

2. A add a squelch control in software so you only hear the audio when there is an actual signal above that threshold. When the radios are squelched suppress direction finding - or at least don't add random positions from the noise floor to the average and power grid. This is needed for intermittent signals like Ham repeaters where the transmitter is not on continuously. Direction indication is only valid when a signal is present.

3. Having to disconnect 4 antennas (optionally connect the terminators) to sync, zero the IQ, and then reverse all of that, is time consuming. The system would be less tedious if you could use PIN diodes to switch the antennas off (to terminators or ground) right on the PCB under software control. The user would never have to disconnect the antennas. Further, Sync and IQ zero could be automated in software.

Thanks for the great product!

rtlsdrblog
Site Admin
Posts: 2428
Joined: Mon Nov 19, 2012 11:54 pm

Re: Feature requests / development ideas

Post by rtlsdrblog » Sun Sep 01, 2019 3:52 am

k5cg wrote:
Sun Sep 01, 2019 2:02 am
More ideas... yes, sorry. After using for a while... so.

1. A way to listen to audio from one of the RTLs (select one or just #1 only) by either a jack on the side of the KerberosSDR housing or from the Pi Audio jack or maybe Bluetooth (to an earpiece or car).

2. A add a squelch control in software so you only hear the audio when there is an actual signal above that threshold. When the radios are squelched suppress direction finding - or at least don't add random positions from the noise floor to the average and power grid. This is needed for intermittent signals like Ham repeaters where the transmitter is not on continuously. Direction indication is only valid when a signal is present.

3. Having to disconnect 4 antennas (optionally connect the terminators) to sync, zero the IQ, and then reverse all of that, is time consuming. The system would be less tedious if you could use PIN diodes to switch the antennas off (to terminators or ground) right on the PCB under software control. The user would never have to disconnect the antennas. Further, Sync and IQ zero could be automated in software.

Thanks for the great product!
Thanks for the ideas, replies below:

1) For this one, we may be able to do this after an upgrade of the software. At the moment the software works in a different way to normal SDR programs, it samples a chunk of data, processes it, then samples again. During the processing time samples are lost. Tamas is working on an upgrade that should allow the full data to be collected.

2) The Kerberos server software is designed to simply output the DOA value, as well as the current power value. It's up to the processing software to squelch based on the power value if necessary. It should be possible to squelch on the server side for audio too.

3) Yes disconnecting the antennas is a hassle. But adding switches, PIN diodes etc has the possibility to corrupt the phase information in the signal. This is why Kerberos uses a directional coupler type of noise injection system. More indepth experiments need to be done with a variety of switch components, to see if any are stable.

In a future SW update, we're going to test automatic DSP notching. So if a narrowband active signal is present in the bandwidth, it can be notched, and ignored during calibration. It won't work if the signal is wideband though.

Future updates will also see a streamlined one click calibration process, that just runs the steps one after another, and checks that the graphs have been zeroed itself.

k5cg
Posts: 13
Joined: Thu Aug 15, 2019 8:52 pm

Re: Feature requests / development ideas

Post by k5cg » Sun Sep 01, 2019 3:45 pm

Excellent! Thanks

GermanTerrible
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Joined: Wed Nov 21, 2018 10:00 am

Re: Feature requests / development ideas

Post by GermanTerrible » Tue Sep 03, 2019 8:34 am

k5cg wrote:
Fri Aug 23, 2019 4:19 am
1. The radius of 4 antennas on the roof in the North/East/West/South arrangement of my car barely fits across the roof (specifically the East to West dimension). Would it be possible to have an option that would allow the array to be rotated 45 degrees so the antennas can be placed in a NW, NE SE, SW (square rather than diamond) pattern? It would fit a square car roof better and provide a larger ground plane for all antennas when using lower frequencies (2m).
Thanks
Perhaps the "manual mode bearing" setting will help you when using compass or GPS as well. I cannot try myself because I have no car of my own. I always work from fixed points.

If it does not work, record a log file as usual. Then try to change "bearing mode" to manual when plotting the log, and set "manual mode bearing" as needed, it could work.

k5cg
Posts: 13
Joined: Thu Aug 15, 2019 8:52 pm

Re: Feature requests / development ideas

Post by k5cg » Wed Sep 04, 2019 8:58 pm

GermanTerrible wrote:
Tue Sep 03, 2019 8:34 am

Perhaps the "manual mode bearing" setting will help you when using compass or GPS as well. I cannot try myself because I have no car of my own. I always work from fixed points.

If it does not work, record a log file as usual. Then try to change "bearing mode" to manual when plotting the log, and set "manual mode bearing" as needed, it could work.
OK I will set the antennas up as I suggested and try Manual mode. Thanks

k5cg
Posts: 13
Joined: Thu Aug 15, 2019 8:52 pm

Re: Feature requests / development ideas

Post by k5cg » Wed Sep 04, 2019 9:03 pm

Another idea...

For the UCA antenna arrangement (maybe ULA also), rather than have to set the lambda in the DOA Estimation page, how about just an entry for the antenna element spacing.

Then have the software figure out the radius. If you change frequencies and don't adjust the antenna spacing then a new lambda is automatically calculated for you.

My point is that the Pi is a computer - so why do I need to get my calculator app out on my phone to determine this number?

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