Yes, it's 345 MHz. Most of the time, no signal is published. This makes sense because the sensor goes years on a battery. It is very reliable.
This may be the FCC application: Honeywell 5800 Series Wireless Technical Specifications - Alarm Grid
At first I didn't think it was, but the above post on Manchester coding says my 128 bits are really 64 bits. So it seams to match the doc. I'll have to read about Manchester coding. Any idea how 16 bit CRC are applied?
I already own an Intel NUC, which I run 24x7 for another purpose. It is a Windows PC. I was originally hoping to use this with the RTL-SDR. It would process the signal with python generated by GNU Radio and run a control app. The RTL-SDR runs hot. I don't really know it's a problem, but am guessing it is not really suitable for 24x7 operation.
It might be better to use a rasp pi rather then an arduino with the radio receiver. The rasp pi could replace the pc and be a standalone controller. Alternately, the arduino could control the radio receiver and send the signal to a PC through the serial port just like the dongle. Probably should just connect the dongle and see how long it lasts. The sensor is made by ademco/honeywell. There is probably a radio receiver IC for this.