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| OK, time to play "identify the QRM" http://www.interceptradio.com/bbs/viewtopic.php?f=26&t=2645 |
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| Author: | John Miles KE5FX [ Wed Feb 25, 2009 8:28 am ] |
| Post subject: | OK, time to play "identify the QRM" |
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. |
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| Author: | N7QOR [ Wed Feb 25, 2009 9:45 am ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
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? |
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| Author: | Rich [ Wed Feb 25, 2009 10:02 am ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
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. |
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| Author: | John Miles KE5FX [ Wed Feb 25, 2009 10:11 am ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
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. |
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| Author: | Rich [ Wed Feb 25, 2009 10:29 am ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
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. |
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| Author: | John Miles KE5FX [ Wed Feb 25, 2009 10:36 am ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
Sounds like that's it, Rich, thanks for the clue! Hosed by my own phone company. Figures... |
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| Author: | Rich [ Wed Feb 25, 2009 8:01 pm ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
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 ! |
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| Author: | John Miles KE5FX [ Thu Feb 26, 2009 5:35 am ] |
| Post subject: | Re: OK, time to play "identify the QRM" |
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! |
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