InterceptRadio.com Forums

Just curious, does anyone know what the strong, relatively constant digital carriers near the right side of this waterfall plot are? Roughly 869.900 to 871.900 MHz, a couple hundred kHz wide. Antenna location is Lake Forest Park.



Seems that a lot of crud has appeared fairly recently in this part of the band, causing some grief to one of my receivers.

My first guess would be, one of Sean's taglines would be correct.

I think it went something like:
"Nextel, its how spectrum gets done"

Just curious, what tools/apps are you using to measure RF and obtain that display?

Not sure who the A-side cell carrier is up there but it might be GSM data. Its probably not Verizon CDMA/EVDO as they run it fixed at 1.23mhz bandwidth.

Yeah, I wondered about some kind of Nextel implementation but the signals are pretty wideband, for voice comms. Was thinking it might be a wireless network for mobile laptops in police cruisers, or some such.

It's a Tektronix 494AP spectrum analyzer running my homebrew waterfall display app through a Prologix GPIB-LAN adapter. The monitor program is actually running on the PC in my office in Kirkland, while the analyzer's at home in LFP.

Keep in mind 869.040 - 893.970 is cellular so its definitely not Nextel.
869-880 is the "A" block of cellular frequencies.

It appears Cingular/ATT is the A-side licensee for the Seattle area:
http://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=11941

...and they are definitely a GSM carrier.

Sounds like that's it, Rich, thanks for the clue! Hosed by my own phone company. Figures...

Your waterfall app looks extremely cool... and I have a Tek 2714/2707 sitting on my desk... might have to put this bad boy to work !

It's kind of a hack, but a useful one. I don't think I've run into the 2707 or 2714 models before, but there are quite a few users running it on 2710/2712 hardware. If they're software-compatible, there'd be a good chance of success. Let me know if you have any luck and I'll add it to the readme file!