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4G Broadband May Jam GPS
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.
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.
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.
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CINC, 4th Penguin Legion
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...
Nearly fifty percent of all graduates come from the bottom half of the class!
You're right. The report is likely to be bogus.
If this is true it means the up and coming cash cow and one of the largest payola maker for representatives is now default for US. Yes, that means UAVs are now unsafe for operation. That also means IFR aviation traffic in inclement weather is many cases is now impossible. It means the entire GPS and navigation markets have been destroyed.
Simply put, if in fact there is any proof that GPS can be compromised by 4G deployment, the FCC will be forced to move 4G to another frequency. Period.
Can you imagine headline, "FCC sued for string of airliner crashes - negligent homicide charges filed against head." And that's just the tip of the iceberg.
No bones about it. *IF* its even remotely true, 4G would be forced to change. Otherwise both safety of the masses and economic damage is just too massive to ignore. Not to mention the possibility of criminally negligent charges.
AM Radio could interfere with aircraft beacons, since they're right next to each other!
Please. We've been allocating spectrum for things for a long time. Interference can be monitored and controlled. Do you really think that mobile telephone companies would put up with broadcasters puking all over their spectrum? Or vice versa? Or either putting up with amateur radio interference?
Or, perhaps worst of all, do you think the Hams would put up with someone interfering with their spectrum? They can triangulate secret government projects accidentally using their shortwave spectrum.
Yes, interference happens from all sorts of places. You'll likely find that devices in your adjacent spectrum are less likely to interfere than other sources of interference.
-- Erich
Slashdot reader since 1997
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.
"A week in the lab saves an hour in the library"
I would stress too much about this. Anything that has even a remote chance of interfering with the US military's use of GPS is never going to be deployed. Period.