4G Broadband May Jam GPS 118
mferrare noted some rumblings that 4G Broadband may jam GPS. There's a slew of technical bits in an report (PDF). 4G broadband frequencies (1525-1559MHz) are next door to GPS frequencies (1559-1610MHz). Test results won't be out until June.
Frequencies? (Score:4, Informative)
All the GPS satellites transmit on the same frequency, 1.575ghz for L1 and 1.227ghz for L2. The only variance from this is Doppler shifts from the user to satellite perspective.
What about all the other RF noise? (Score:5, Informative)
Don't worry about bandwidth overlap (guaranteed to happen with some poorly designed transmitters and antennas) worry about all the other electronic devices which aren't meant to transmit RF but blast it out all over the bands.
I have recently got into amateur radio and some bands are locally unusable due to something as simple as a transformer power supply blasting out many watts of RFI.
The slow death of radio bands to RFI is like the "death" of stargazing due to light pollution.
Re:FCC approved this? (Score:5, Informative)
Feh. It wouldn't be the first time these dimwits at the FCC screwed up. I remember installing 928.8... MHz SCADA (you know, the telemetry that runs your water, electricity, gas...) and it worked great. About nine months later, the FCC allowed 929 MHz paging. In a very short span of time we had enough energy coming down the antenna line to light a neon bulb. They were licensed for 3 kW ERP. Our remotes were licensed for 5 W + some gain from a small Yagi.
The master receivers went deaf from the continuous blast of high powered paging traffic. A Cavity filter can't do much to get rid of strong signals only 200 kHz away at 900 MHz.
Yeah, the FCC screwed up. They had no knowledge of the state of the art of receivers. We bought receivers engineered for sensitivity, not strong signals, because at the time, there were no other significant strong signal sources on that band. The state of the art took a while to catch up. We ended up solving the problem by re-licensing our channels for horizontal polarization. The pager stuff remained vertical. We got 20 dB of immunity from them and that was enough.
And to the jerkwads at the FCC who thought this was acceptable: DO YOU LIKE WATER? DO YOU LIKE ELECTRICITY? DON'T DO THIS TO US!
spit...
Not all 4G (Score:5, Informative)
Contrary to what the headline and summary implies, "4G" doesn't always use 1500Mhz. In fact, I'd never heard of a 1500Mhz cellular network until now. Apparently a startup called "Lightsquared" has bought that patch of spectrum and wants to roll out an LTE network. No other 4G network is in that frequency range. For example, Verizon's LTE network is at 700Mhz and Sprint's Wimax network is 2500Mhz.
So, really, this is no concern to anyone but Lightsquared. Either there's no interference and they can go ahead with their rollout, or there is interference and the FCC has to step in. In either case, the other 4G networks are unaffected.
Re:This just in... (Score:3, Informative)
>>AM Radio could interfere with aircraft beacons, since they're right next to each other!
These intentionally overlap. Back in the day, AM radio stations were just as useful at navigation as proper NDBs. You can tune in and listen to most of the AM band using your aircraft's (very old) ADF.