[gabrielblack]

Exactly, I've a "premium" RTL-SDR and I se only the traffic on 900 MHz band. A more expensive SDR is required to sniff seriously. This is amateur hardware, professional hardware ( as the models described in the Snowden's documents ) can reach 100k E or more. That hardware can elaborate every frequency, more frequency in parallel with maximum reliability, a 20$ hardware simply can't. A good compromise can be one of the commercial SDR like Lime, etc.