Hi all. I’m an amateur embedded engineer, but a newb to SDR and RF in general.
I have a niche use case for a volunteer group I work with; we need to get the rough location of a tight cluster (<50m radius) of around 30 to 50 mobile phones in a rural area. The phones will likely have a tower connection, but not particularly actively used. I’m hoping to do this within a distance of 10km.
I can’t find any other threads on a subject like this, and can’t really tell if it’s possible with some coding, so I’m hoping I can get a good answer here!
Getting an RTLSDR to get used to SDRs in general this week, with the hope of getting hold of a krakenSDR in a couple of months if it fits the above role.
The Kraken’s upper frequency limit is 1766 MHz. Cell phone frequencies in the USA are mostly in the 850-900 MHz, 1800 MHz and 1900 MHz ranges for 3G or 4G phones, but 5G can go up into the 24 GHZ and higher ranges. So, you might want to do some work with a SDR or TinySA (spectrum analyzer) do determine what frequencies the local cell tower is using before buying a Kraken. Since you said “10km” I’m assuming you’re not in the USA, so you’ll want to research what frequencies are used in your area, and hopefully determine both the transmit and receive frequencies, so you can set the Kraken up to the phone transmit / tower receive frequency and not the tower transmit frequency!
To pick up a cell phone signal from that distance, you will need to position your self on high ground, not down in a valley, and while many or most of here on this forum are chasing people with 5 watt and higher transmitters, you’re looking for just 1-3 watt signals, at a distance of 10km, that’s a very, very tiny signal!
Thanks, apologies should have specified, this is in the UK.
Yes, have an SDR showing up today so I can get to grips with the basic concepts of SDR.
The ground around here is very flat, so I’m hoping that roof mounting on a car will be able to accomplish this as I won’t realistically be able to reposition to high ground to get signals.
Tower positions and frequencies in the UK are quite well documented via databases like netmonster, so I’m hoping I’ll be able to dynamically isolate cells from phones this way.
Thanks. however my understanding is that the Kraken can also be used just RSSI to create rough heat maps over a certain area. there’s absolutely no intention or need to differentiate receive or decode individual signals, Only Roughly identify the location of large clusters nearby.
If the cell phones happen to be transmitting all at around the same uplink frequency, and there are no other cellphone clusters in the area that could interfere, it may be possible.
The cluster signal would probably dominate any isolated cell phones. But different carriers use different frequencies, and even on the same carrier the uplink frequency is not guaranteed to always be the same.
Most importantly, the uplink frequency would need to be below 1.766 GHz, which is the upper range of the KrakenSDR.