Hacker News Reader

Why do you need Tx for an IMSI catcher? Also, a USB TV tuner won’t work for the receiving side either. You’ll need to step up into an actual proper SDR for that. Still easily sub $500, but sub $100 is a bit too far a stretch.

Easier if your target phone connects to you.

A $12 RTL-SDR USB stick will 100% work for most GSM rx (won't hit the 1900+MHz bands without a downconverter, but that's why you want tx - you'll use it to force the phone onto the 800-900MHz bands anyway, the top half of the 915MHz ISM band in the US if you have a HAM licence and are trying to not break _too_ many laws at once).

This DefCon talk: https://www.youtube.com/watch?v=fQSu9cBaojc

Gives a good overview of why you need tx to capture an IMSI - without forcing a handset into transmitting non-encrypted, you only get the TMSI (unless you can crack the crypto - and why bother, when a base station can instruct a handset to just not encrypt anything?)

You still need reliable clock sync / latency. Otherwise you can just announce, not communicate bi-directionally.

As I understand it, these VGA adapters need the bandwidth of USB 3 to function. Raspberry Pi only has USB 2 ports.