
FCC to Investigate Raised RF Noise Floor - nvk
http://hackaday.com/2016/06/21/fcc-to-investigate-raised-rf-noise-floor/
======
kazinator
I experience crappiness in guitar tone that follows a very rigid weekly
pattern. For instance, the rig reliably puts out amazing "mojo" Sunday
evenings. Every Monday morning, there is something somewhat displeasing and
blatty in the tone that cannot be EQ'd out.

High gain distortion are susceptible due to their nonlinearity. Any RF mixing
in there gets modulated down into the audio band. I greatly improved the issue
with ferrite beads, but not 100%.

Not all music equipment has good defenses against the ingress of RF. Shunt
capacitors on inputs are often omitted, and series inductors are rarely used.
The grounding isn't the best: often, unbalanced input and output jacks have
ground connections to the audio circuit board, rather than to a Kelvin ground
at the power supply. RF can get into the board via that path.

~~~
rconti
Enjoying all the interference Sunday nights when everyone's home watching TV,
but when everyone leaves for work Monday morning, there's less pleasing
interference? :)

~~~
kazinator
It's different if you live in an area where everyone comes _to_ or _through_
on Monday morning.

------
nikanj
Do the regulations really work anyway, in this world of Walmart and Alibaba?

~~~
krastanov
I can imagine a public or private entity that goes around and fines people
that do not switch off bad equipment and fine the manufacturer (or bar them
from doing business in the country).

~~~
nikanj
The manufacturer is often nearly impossible to find, and they're not doing
business in the country, some enterprising ebay power seller is.

Baby monitors, wireless yard cameras etc are often absolute garbage from an RF
point of view, and sold with brand names such as "best for baby". Good luck
trying to nail that company.

~~~
ubernostrum
The FCC's mandate isn't to stop everyone everywhere in the world from
producing crap $5 baby monitors that spew noise on the whole spectrum. Their
mandate is to keep those crap baby monitors out of the US and off US markets.
Which they can do relatively easily; even if the manufacturer is hiding behind
seven proxies, twelve shell companies and sourcing from two dozen countries,
those baby monitors still had to get into the US at a particular port of
entry, had to be sold by someone who had the ability to take payments from and
arrange delivery to people in the US, etc., and that's going to point to
someone the FCC can happily issue big fines to, discouraging them from
continuing to import/sell the devices.

~~~
ultramancool
There are literally dozens of sites you can buy cell jammers from, pay with
PayPal and get it in the mail a few weeks later. The mail is really not
checked for this kind of violation very often.

Who are you going to sue if I order a cell jammer from a China or Hong Kong
based company and your own governmental postal service delivers it to me? How
about if it's just a crappy or malfunctioning device that leaks and I have no
knowledge of it?

It's a very difficult thing to police... almost approaching war on drugs
territory.

~~~
GrumpyYoungMan
The fine and jail time apply to the person operating the jammer. By the way,
these "dozens of sites" are all too happy to turn over purchase records to law
enforcement if asked.

As for "it's a very difficult thing to police", a jammer is a _transmitter_ ,
one that's powerful enough to drown out the signals it's designed to jam.
Turning one on is like turning on a giant flashing billboard saying "ARREST
ME" over your head; it's easy to follow the jamming signal back to the source
with the right equipment, which, of course, the FCC and similar agencies have
plenty of.

Want some examples?

"FCC Proposes $29K Fine For Employer That Jammed Employee Cell Phones"
[https://www.fcc.gov/document/fcc-proposes-29k-fine-
employer-...](https://www.fcc.gov/document/fcc-proposes-29k-fine-employer-
jammed-employee-cell-phones)

"Florida Man Gets $48K Fine From FCC For Using Cell Phone Jammer"
[http://www.techtimes.com/articles/161146/20160526/florida-
ma...](http://www.techtimes.com/articles/161146/20160526/florida-man-
gets-48k-fine-from-fcc-for-using-cell-phone-jammer.htm)

"FCC Fines Operator of GPS Jammer That Affected Newark Airport GBAS"
[http://www.insidegnss.com/node/3676](http://www.insidegnss.com/node/3676)

"Man arrested for allegedly using cell phone jammer on train"
[http://www.cnet.com/news/man-arrested-for-allegedly-using-
ce...](http://www.cnet.com/news/man-arrested-for-allegedly-using-cell-phone-
jammer-on-train/)

------
w8rbt
This can be fixed, however, electronics will cost more when properly designed
and filtered. Until interference impacts a lot of people (not just hams and
OTA TV viewers) no one will care enough to do anything about it.

~~~
maxerickson
Only if they realize it is a problem. I did a short term thing where I was a
passenger with someone that was on the road all the time. They had no idea
that their Walmartian USB power adapter was blowing out radio reception until
I unplugged it.

------
coroutines
My grandfather has a theory that it's the PG&E Smart water meters that have
been rolling out that's doing this...

I'm not a radio guy, so I don't know how plausible that sounds.

~~~
raverbashing
If they really got smart water meters that don't follow FCC regulations,
they're in for a bad time

------
yyyuuu
Sorry for my ignorance, but How will extreme levels of RF noise disrupt the
modern day life?

~~~
lostlogin
If the MRI engineer we use is to believed, us leaving the scanner door open by
accident led to a very grumpy letter to the MR vendor by the coast guard. 3T
so I'm guessing 128ish MHz, I'll let someone else judge if this story is bs.

------
grandalf
I posted this the other day, looks like it missed dupe-detection ?
[https://news.ycombinator.com/item?id=11946490](https://news.ycombinator.com/item?id=11946490)

------
fit2rule
Wait, isn't this all free energy, waiting to be harvested?

~~~
cbd1984
Yes, which raises one possible way of fighting it: Make electronics
manufacturers adhere to power efficiency ratings. The moment they have to care
about how power efficient their gear is, they'll look at everywhere power's
being wasted by, I don't know, being broadcast into the air for absolutely no
good reason.

~~~
MertsA
That's probably not going to be effective. Look at devices with cheap
universal motors and the like. They spew out tons of noise and a lot of them
have a filter on the input to cut down on noise but as far as decreasing
wasted power, the RF noise is a tiny drop in the bucket compared to the total
power of whatever power tool or vacuum we're talking about. Also, the filter
that they put on the input to try to combat this doesn't increase the
efficiency of the device. If anything, I'd be afraid that there would be
design changes to decrease the thermal losses of a device even if it increased
the noise it put out.

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nxzero
Seems like the NSA would have all the data the the FCC needs, is this right,
or no?

~~~
ConroyBumpus
Funny, but incorrect. This mostly has to do with spurious RF noise generated
by badly engineered devices like power supplies or manual light dimmer
switches - things that aren't designed to communicate. Manufacturers are
supposed to test for these sorts of emissions, but frequently don't.

~~~
nxzero
Meaning you're claiming in a cities NYC & DC that the NSA doesn't to full
spectrum dumps, right? Or that they would have not looked into statistically
unusual high amounts of background noise?

If the NSA does this, they'd have the info. If they don't, I'd be curious why;
meaning legal, physical limits, etc.

------
zaroth
How can this be a real problem with exponential signal loss over distance?
Sure, two devices in close proximity may interfere with each other. But that
is in no way a "noise floor issue which will render certain frequencies
unusable."

~~~
krastanov
Signal strength does not decay exponentially, rather as distance^-3 for a
dipole[1]. Most noise sources are probably well approximated by a dipole
antenna[2]. Some fancy modern modulation scheme with extremely dense encoding
of information might suffer stronger decay, but the article is about simple
sources of noise, not about modern modulation schemes.

[1]:
[https://en.wikipedia.org/wiki/Dipole#Vector_form](https://en.wikipedia.org/wiki/Dipole#Vector_form)
[2]:
[https://en.wikipedia.org/wiki/Dipole_antenna#Hertzian_dipole](https://en.wikipedia.org/wiki/Dipole_antenna#Hertzian_dipole)

~~~
Bromskloss
> rather as distance^-3 for a dipole

Wait a minute. The radiated power in the far field goes like r^-2, right?

~~~
kqr
This is my intuition as well, because at a distance _r_ around the source you
have a sphere, and the area of the sphere will relate to the radius _r_ as _r_
^-2.

That said, the equation linked in the comment does indeed contain an r^-3
factor. I don't know if it's cancelled out by something else – my physics game
isn't strong enough.

~~~
Bromskloss
The expressions for the field include terms of different powers of r. At large
distances (compared to the wavelength) from the transmitting antenna, only the
r^-1 terms (which dies off with r more slowly than the others) remain with any
appreciable strength. This is called the "far-field". The power per cross-
sectional area is proportional to E·B (or, equivalently, to E^2 or to B^2),
and therefore goes as r^-2.

------
teraformer
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.

~~~
Animats
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-c...](http://www.edn.com/design/test-and-
measurement/4412405/Low-cost-spectrum-analyzer-product-roundup)

~~~
VLM
>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.

Um, yeah, about that, that would be really nice if it were true. Maybe
sometimes for some hardware in some situations. For a 1st gen motorola droid X
I can personally guarantee when the wifi gets unusually frisky the bluetooth
drops out. Very annoying when listening to music on a BT earpiece. A hardwired
headphone never drops out, but a main marketing point of USB-C is to get rid
of headphone jacks because they work well and they're too cheap to profit off.

The cable leakage thing was true in the 80s, but the FCC wisely put pretty low
transmit level limits on all the two-way gear (settop boxes, cablemodems,
cable phone modems). To make a long story short if signals are getting out,
interference is getting in and is measurable and is likely causing an
upload/upstream problem. If you think microwatts of output power from a
cracked cable is annoying to a fm radio listener, imagine a "miles long" cable
with a crack acting like an antenna across the street from a 50 kilowatt am
transmitter and consider its effect on modem upstream speeds. Problems will
happen, but it'll get fixed pretty fast, unlike the 80s or something. Maybe a
decade ago the journalists made a sport of complaining about digital phone
service being unable to dial 911 and that was the end of unrepaired cable
leakage problems.

~~~
kqr
> when the wifi gets unusually frisky the bluetooth drops out

Oh so _that_ is why my bluetooth audio gets choppy when I walk past the wifi
access point in the hallway? I've never even thought about that before other
than been annoyed by it.

How utterly inconvenient that they occupy the exact same frequencies. I should
probably get a 5 GHz wifi access point...

~~~
cmdrfred
Upgrading to 5ghz is worth it. My latency was cut in half.

~~~
kqr
My issue is money and space. I'd like to cram it into the same tiny little box
that already houses the fibre-to-ethernet converter as well as the router. I'm
also not sure if it would penetrate the walls and reach all rooms.

