scanning 72 - 76 MHz, wireless clock system

[parnass]

I've been receiving data signals on 72.16, 72.22, 72,26, 72.30 MHz and a few other frequencies which sound similar to each other. It is a screeching sound, reminiscent of shortwave WEFAX signals, but with a 5-beat sequence which repeats atop the screeching.

Here is a sample of the signals I hear: http://parnass.com/articles/primex-clock.wav

An FCC license in the Industrial/Business Pool, WQBQ861, permits my local school district to operate several 0.7 to 1 watt transmitters on these frequencies.

The signals are apparently used to synchronize a GPS-based wireless clock system. You can read more about wireless clock systems here: http://www.primexwireless.com/uploads/files/GPSTime.pdf

The article explains:

"...With the Primex Wireless system, the GPS signal is locally rebroadcast in a building at a 72.1- to 72.4 MHz frequency that is less prone to noise signals than the WWVB broadcast frequency of 60 kHz and more easily penetrates walls and metal structures. The GPS signal is also less affected by weather conditions, and the receiver can pick it up anywhere in the world..."

The FCC license database shows that systems like this are widespread so you can probably hear similar signals in your area. Many of the FCC license entries refer to using the Primex Wireless system.

 

[DaveNF2G]

Neat. Another home decoding project for some budding software author.

 

[Dispatrick]

I remember a few years back when I got my BC346XT I was scanning above 54MHz and all the bands that my old scanner never had access too, I picked up these channels and posted about them on here. I still pick them up. Do you live near a large office building and/or hospital? The ones I receive are from the hospital that I live close by to. they use them to sync all the clocks through out the facility.


BTW, I did see these clocks on Ebay for no more than 50 bucks if you are interested

 

[parnass]

... Do you live near a large office building and/or hospital? ...

BTW, I did see these clocks on Ebay for no more than 50 bucks if you are interested

Thanks for your comments. The 72 MHz Primex Wireless systems are apparently in use in several locations across the country.

There are two schools closer to my home than the nearest hospital which is in another county. One of the schools is atop a hill and visible from my back yard. The schools are FCC licensed on the frequencies I monitored.

I saw those Primex Wireless clocks on eBay and Primex Wireless has a couple of videos explaining their system on Youtube.com

Another person reported that the Primex transmitter he installed was higher power. It ran 30 watts output in order to synchronize clocks in multiple buildings on a college campus. However, a sampling of FCC licenses shows 1 watt transmitters are the norm.