Advice for tracking intermittent signal

Discuss KerberosSDR - 4x Coherent RTL-SDR
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Advice for tracking intermittent signal

Post by TowerGuy100 » Tue May 05, 2020 8:49 pm

So I have successfully tracked a continuously operating transmitter, which was fun. However, more common is tracking an intermittent signal. I tried tracking a DMR transmitter that would key for about 5 seconds every minute or so. The compass has minimum settings for power and DOA Confidence, which seem to work well.

I tried using the same settings in the mapping app, but I saw results appearing even while the transmitter was not keyed. This resulted in the heat map and the predicted location to keep showing in the wrong area.

Should those settings in the app work like for the compass? Should I start and stop DOA via the icon on the map in the app as the transmitter starts/stops?

Any suggestions for getting better results with non-continuous transmitters?



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Re: Advice for tracking intermittent signal

Post by rtlsdrblog » Wed May 13, 2020 6:20 am

Intermittant signals are currently a challenge for the KSDR. The KSDR samples a block of data, and then processes it in the DSP code. While it's doing the DSP it cannot continue sampling, so it drops data. If your signal was TX'd during the dropped data period it would be lost.

We've still got code in the works that will squelch data at the lower data acquisition levels, which would solve this issue. It's still being tested, but it should be ready for a beta release in a few months.

For now you need to run the KSDR on the fastest machine you can get, and try to get the update rate as fast as possible.

In the file, you can also try editing the BUFF_SIZE parameter, and changing it to 128. This will reduce the block size, resulting in a faster update rate. Make sure you're using the latest image file if you're using a Pi4 which has a much faster update rate.

The app squelch settings should work the same, although the compass squelch was coded by a community member, so i'm not sure if it's exactly the same.

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Re: Advice for tracking intermittent signal

Post by SIGINT » Sun Sep 13, 2020 10:13 pm

I have only had the KerberosSDR for a few days - and have issues too with short bursts of signals - like DMR Beacons.

However - after upgrading from a Raspberry Pi 3 to a 4 - several things have improved a LOT:
- Sync now takes just a few seconds
- I can capture much shorter signals - and it appears that the Incident Angle display jumps less around.

One question on that display: It shows 0-360 degrees - in relation to what ? - For a certain signal, the IA display on the Kerberos SDR application typically shows about 110 degrees.

The Android app however, points to around 225 degrees with the same signal

My initial impression was that the degrees shown on the IA display was alligned with North - if Antenna 1-3 were pointing N-S ?

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