5 ms·

Gee, I wonder if it has anything to do with cell phones, and in particular, the high bandwidth data consumption of smart phones. Look toward a city skyline at

Gee, I wonder if it has anything to do with cell phones, and in particular, the high bandwidth data consumption of smart phones. Look toward a city skyline at night. Or even a small town. You'll see a blended haze of light reaching up into the sky. Probably a similar deal with the general radio spectrum emissions, now that everyone's carrying the equivalent of pocket RF flash lights, and walking in proximity to the RF street lamps that cell phone towers have become.

tlrobinson 10y ago
Even non-radio devices like lighting ballasts, solar panel charge controllers, inverters, etc can cause lots of noise.
LeoPanthera 10y ago
I'm a radio ham. No, it has little-to-nothing to do with smartphones, which are incredibly tightly regulated and operate in very tightly defined bands of the EM spectrum. My guess (and it is only a guess) is that the problem is mostly from unregulated imported electronics that emit all kinds of broadband RF noise as a consequence of being made cheaply.
- deleted 10y ago
  [deleted]
friendzis 10y ago
Continuing your analogy, cell phones are like supermarket barcode scanners: weak and clearly red. It does not really matter how many of them you cram into a room, you can still send morse code with a green laser. All devices have small daylight lamp attached to them, the power of which is rather strictly regulated (IEC-61000, if anyone is interested). If you cram a lot of them into a room, morse coding with that green laser becomes difficult. You could increase power/brightness of the laser and call the problem solved. But then try to measure brightness of your lighting fixtures - becomes quite difficult. So no, proliferation of cell phones is only a problem for cell phones (one of the reasons for migrations 2G -> 3G -> 4G). The real problem are other devices transmitting in cell phone spectra effectively DDoS'ing them.
Animats 10y ago
Cell phones are running several receivers at the same time they're transmitting. The Bluetooth, GPS, WiFi, and GSM receivers all have to receive cleanly while the Bluetooth, WiFi, and GSM transmitters are transmitting. It's amazing that this works. Spurious RF noise from any of those transmitters would interfere with the receivers only a few millimeters away. So cell phone designers have to put effort into getting RF isolation right. Computers were once big RF emitters, but the FCC cracked down on that successfully in the 1980s. In the early days of personal computing, a Radio Shack TRS-80 and a Milton Bradley Big Trak would both crash if close. In recent years, most computers got radio receivers for at least WiFi, and thus had to be built well enough not to knock out their own receivers. Analog TV sets tended to emit loudly at the local oscillator frequency. The UK used to drive around with "television detector" vans to find people who didn't pay their TV tax, which funds the BBC. But tuners quieted down years ago, as they became tiny RF-tight sealed units. The worst behavior comes from switching power supplies, especially for lighting. The cost pressure is very high. They don't receive, so they have no receiver to protect. Another big source of noise is leaky cable TV systems. Again, since they don't receive, they aren't affected by their own leakage. The cable industry has successfully lobbied to escape tight restrictions on cable system leakage. Those two sources are probably the source of most problems. Low-cost spectrum analyzers are available, and some are laptop peripherals.[1] There are ones as cheap as $69 on eBay, but the consensus in EDN is that you have to pay a few hundred dollars to get something that produces useful measurements. People who install and maintain WiFi networks in large buildings usually have one. Then you can find what's blithering all over the spectrum. [1] http://www.edn.com/design/test-and-measurement/4412405/Low-cost-spectrum-analyzer-product-roundup http://www.edn.com/design/test-and-measurement/4412405/Low-c...
- jahnu 10y ago
  TV detector vans, despite being theoretically possible to build, are a myth and just propaganda spread by the TV license collection agency. At most they drove around in vans with some random gear in it as PR stunt.
- cbd1984 10y ago
  > Analog TV sets tended to emit loudly at the local oscillator frequency. The UK used to drive around with "television detector" vans to find people who didn't pay their TV tax, which funds the BBC. But tuners quieted down years ago, as they became tiny RF-tight sealed units. CRTs used to emit the picture on their screen well enough you could receive it over a nontrivial distance. This is called Van Eck phreaking. https://en.wikipedia.org/wiki/Van_Eck_phreaking https://en.wikipedia.org/wiki/Van_Eck_phreaking OTOH, being able to receive a signal and being able to nail down where it's coming from and who's broadcasting it are two very different things, and the location part is substantially harder. Using the Van Eck technique, or any other, to crack down on people not paying the BBC license fee would have cost more than the fee was worth. Psychological ploys with faked-up vans, however, are a lot cheaper, and can be fairly effective.
noonespecial 10y ago
Its almost always crappy switching power supplies like that $5 ebay "Abble" charger that seemed like such a deal.
cbd1984 10y ago
Any gear which makes battery life a selling point will look hard at every RF emanation it makes and cut the noise. I'd look at things plugged into walls before anything running off a battery.

tlrobinson 10y ago

Even non-radio devices like lighting ballasts, solar panel charge controllers, inverters, etc can cause lots of noise.

LeoPanthera 10y ago

I'm a radio ham. No, it has little-to-nothing to do with smartphones, which are incredibly tightly regulated and operate in very tightly defined bands of the EM spectrum. My guess (and it is only a guess) is that the problem is mostly from unregulated imported electronics that emit all kinds of broadband RF noise as a consequence of being made cheaply.

deleted 10y ago
[deleted]

friendzis 10y ago

Continuing your analogy, cell phones are like supermarket barcode scanners: weak and clearly red. It does not really matter how many of them you cram into a room, you can still send morse code with a green laser. All devices have small daylight lamp attached to them, the power of which is rather strictly regulated (IEC-61000, if anyone is interested). If you cram a lot of them into a room, morse coding with that green laser becomes difficult. You could increase power/brightness of the laser and call the problem solved. But then try to measure brightness of your lighting fixtures - becomes quite difficult. So no, proliferation of cell phones is only a problem for cell phones (one of the reasons for migrations 2G -> 3G -> 4G). The real problem are other devices transmitting in cell phone spectra effectively DDoS'ing them.

Animats 10y ago

Cell phones are running several receivers at the same time they're transmitting. The Bluetooth, GPS, WiFi, and GSM receivers all have to receive cleanly while the Bluetooth, WiFi, and GSM transmitters are transmitting. It's amazing that this works. Spurious RF noise from any of those transmitters would interfere with the receivers only a few millimeters away. So cell phone designers have to put effort into getting RF isolation right. Computers were once big RF emitters, but the FCC cracked down on that successfully in the 1980s. In the early days of personal computing, a Radio Shack TRS-80 and a Milton Bradley Big Trak would both crash if close. In recent years, most computers got radio receivers for at least WiFi, and thus had to be built well enough not to knock out their own receivers. Analog TV sets tended to emit loudly at the local oscillator frequency. The UK used to drive around with "television detector" vans to find people who didn't pay their TV tax, which funds the BBC. But tuners quieted down years ago, as they became tiny RF-tight sealed units. The worst behavior comes from switching power supplies, especially for lighting. The cost pressure is very high. They don't receive, so they have no receiver to protect. Another big source of noise is leaky cable TV systems. Again, since they don't receive, they aren't affected by their own leakage. The cable industry has successfully lobbied to escape tight restrictions on cable system leakage. Those two sources are probably the source of most problems. Low-cost spectrum analyzers are available, and some are laptop peripherals.[1] There are ones as cheap as $69 on eBay, but the consensus in EDN is that you have to pay a few hundred dollars to get something that produces useful measurements. People who install and maintain WiFi networks in large buildings usually have one. Then you can find what's blithering all over the spectrum. [1] http://www.edn.com/design/test-and-measurement/4412405/Low-cost-spectrum-analyzer-product-roundup http://www.edn.com/design/test-and-measurement/4412405/Low-c...

jahnu 10y ago
TV detector vans, despite being theoretically possible to build, are a myth and just propaganda spread by the TV license collection agency. At most they drove around in vans with some random gear in it as PR stunt.
cbd1984 10y ago
> Analog TV sets tended to emit loudly at the local oscillator frequency. The UK used to drive around with "television detector" vans to find people who didn't pay their TV tax, which funds the BBC. But tuners quieted down years ago, as they became tiny RF-tight sealed units. CRTs used to emit the picture on their screen well enough you could receive it over a nontrivial distance. This is called Van Eck phreaking. https://en.wikipedia.org/wiki/Van_Eck_phreaking https://en.wikipedia.org/wiki/Van_Eck_phreaking OTOH, being able to receive a signal and being able to nail down where it's coming from and who's broadcasting it are two very different things, and the location part is substantially harder. Using the Van Eck technique, or any other, to crack down on people not paying the BBC license fee would have cost more than the fee was worth. Psychological ploys with faked-up vans, however, are a lot cheaper, and can be fairly effective.

noonespecial 10y ago

Its almost always crappy switching power supplies like that $5 ebay "Abble" charger that seemed like such a deal.

cbd1984 10y ago

Any gear which makes battery life a selling point will look hard at every RF emanation it makes and cut the noise. I'd look at things plugged into walls before anything running off a battery.