To find the frequency of the peaks
i measured on the Esmog Spion,
i bought a RTL-SDR kit for 22€ ($26.95).
range: 25MHZ tot 1.7GHz.
i'm an amateur, i don't know if this
thing is very useful, but it shows peaks
at 169 MHz (paging) perfectly matching the Esmog Spion peaks
seen in my TETRA video.
I installed this device in 5-10 minutes
following the walk through on their website.
The "rtlsdr-scanner" software is useful for scanning a range.
I scan a range for example between 100MHz to 200MHz
This takes my computer about 2 minutes. It took me about an hour to scan the entire range of the dongle. Scanning a too wide range at once gives me an error, so this is why i do it in smaller parts. Before starting a new scan i restart the software, because it otherwise doesn't scan the new range. i'm missing why that is.
Intermittent peaks (like the paging) can be missed. because the software takes a snapshot, and if the peak isn't there it won't catch it. Possibly with settings or other scanning software it can be catched every time.
You can zoom in and out and do some manipulations on the result of a scan.