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Was doing some SDR scanning tonight and came across a bunch of strong signals in the 72Mhz band. The data signal is a MFSK-like signal with a bandwidth around 300hz wide, roughly 35 baud.

So apparently these are quite popular. Companies have a GPS-based receiver on the roof with a 72Mhz RF transmitter which can be picked up by digital clocks around the campus and/or other time-sensitive equipment.

Here's a company that sells the gear:

https://www.primexinc.com/clocks/xr-series/

Looks like the signals from around here were coming from Children's Hospital --> http://wireless2.fcc.gov/UlsApp/UlsSear ... ey=3118403

The RF power output can vary from 1W, 5W or 30W -- at least the model from the above company.

Oddly, the Children's transmitters stopped at 1AM local time. EDIT: They came back on at 1:40AM. Possibly only on for 20 min or so?

Did a wider FCC search and quite a few companies are using these GPS-clocks.

If anyone knows a decoder tool that information would be much appreciated.

Here's a screenshot of the signal:

I find these up in various mechanical rooms at times. Hospital in Port Townsend, many schools..

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