I'm just kind of learning this, so take the following with lot's of
salt.....comments and criticism welcome
Seems to me the problem is that they are leaking high frequency noise in the
AM spectrum and NOT in theFM.
Not an expert, but academically, seems to me a good Faraday cage and more
shielding might be the answer, rather than justgetting rid of AM. Bare
unshielded wires are going to send out a lot of radiation at whatever frequency
they operate at.
Interesting about the old claim that FM is inherently better than AM. I
think that might be an oversimplification.
AM travels long long distances (because the wavelength is used is better to
reflect off the upper atmosphere.) FM can'tdo that. So the SNR (signal to
noise ratio) for FM is very very high for longer distances because the signal
will be so weak.
So it's not that crackly FM doesn't happen. It's just that people don't even
bother trying to listen it's so bad.
It is better than AM for short distances, but that's only at the same wattage.
Also the bandwidth used for FM radio stations
is greater than AM radio bandwidth, and this has a lot to do with SNR ratios
as. It should be obvious that you can cure any SNR problems with stronger
signal. but because of the fact that AM travels so well, makes that
problematic as for station to stationinterference.
At some level the distinction between AM and FM is also a little contrived.
AM also varies the frequency as exploited in single sidebandreceivers. Any
varying wave will have have a frequency spread. So at some level, AM is also
a form of FM.
I think Armstrong's old demonstrations with a tesla coil showing static on AM
and not on FM, were probably more than a little
disingenuous as tesla coils operate at AM frequencies.
From wikipedia:
In 1922, John Renshaw Carson of AT&T, inventor of Single-sideband modulation
(SSB modulation), had published a paper in the Proceedings of the IRE arguing
that FM did not appear to offer any particular advantage.[15] Armstrong managed
to demonstrate the advantages of FM radio despite Carson's skepticism in a
now-famous paper on FM in the Proceedings of the IRE in 1936,[16] which was
reprinted in the August 1984 issue of Proceedings of the IEEE.[17]Today the
consensus regarding FM is that narrow band FM is not so advantageous in terms
of noise reduction, but wide band FM can bring great improvement in signal to
noise ratio if the signal is stronger than a certain threshold. Hence Carson
was not entirely wrong, and the Carson bandwidth rule for FM is still important
today. Thus, both Carson and Armstrong ultimately contributed significantly to
the science and technology of radio. The threshold concept was discussed by
Murray G. Crosby (inventor of Crosby system for FM Stereo) who pointed out that
for wide band FM to provide better signal to noise ratio, the signal should be
above a certain threshold, according to his paper published in Proceedings of
the IRE in 1937.[18] Thus Crosby's work supplemented Armstrong's paper in 1936.
From: brucedp5 via EV <ev@lists.evdl.org>
To: ev@lists.evdl.org
Sent: Wednesday, February 10, 2016 12:16 AM
Subject: [EVDL] EVLN: Why Electric Cars Are Ditching AM Radio
'EV owners Want Their AM Radio Back'
http://motherboard.vice.com/en_uk/read/why-electric-cars-are-ditching-am-radio
Why Electric Cars Are Ditching AM Radio
5 February 2016 MEGHAN NEAL
[image
https://lh5.googleusercontent.com/vzU_4bnWa0HQghXTUYtx933Gflhnp2xupQKxmpY2JdpgQuGhMQ8eIJiK4h3gv851Ym372AdcPfPGzr5UrJO6a521OhvpWpC2WR4riM6ROvb5a--5J-zO9e6_xUbHOGI5D-N0YTEq
Screenshot via Tesla Motors Club
]
Electric cars may be energy efficient Earth-saving futuremobiles, but their
rise could also have a strange unintended consequence: killing off the
oldest form of radio.
Two popular electric cars, the BMW i3 and Tesla Model X, are ditching
terrestrial AM radio because electromagnetic noise from the electric motor
interferes with the broadcast reception, causing static, as the blog Music
3.0 recently pointed out.
Electronics have always been a source of AM radio static, and electric
motors are no exception. EVs are powered by a rechargeable battery, electric
motor, and a frequency converter that controls how much power the car's
electrical motors put out by turning voltage on and off thousands of times a
second, basically chopping up energy. This process causes electromagnetic
interference that gets picked up by the radio.
AM radio has always been more susceptible to static than its partner on the
dial. "AM" stands for amplitude modulation, which means the height of the
radio waves are varied over time to encode the information, versus “FM,”
frequency modulation, which varies their speed. Since amplitude, not
frequency, is affected by electrical noise emitted by gadgets like
smartphones, TVs, computers, even vacuum cleaners and hairdryers, AM signals
are prone to distortion and crackling.
That crackle apparently just doesn’t fly with luxury auto brands. BMW
spokesperson Rebecca Kiehne told me, "Electric motors cause interference on
AM which is why BMW decided to remove this option. While it could be
offered, BMW's performance standards are very high and we don't offer a
product that meets less than those high standards."
But while BMW disabled AM radio in the i3 because the company was worried
customers would complain about the poor sound quality, some customers have
instead taken to complaining about the lack of AM radio. Consumers took to
forums to bemoan the omission, a few even saying they wouldn’t buy an i3
without it. One BMW owner commented, “I plan to drag out my portable AM
radio and leave it in the car.” Some owners are hacking the car to get AM
radio back.
Meanwhile, the new Tesla Model X also dropped terrestrial AM radio from its
infotainment dashboard—a change from the Model S. Instead, you can get most
AM stations via internet radio if you go menu diving through TuneIn, a
service that aggregates internet radio and traditional AM/FM stations and is
the standard radio option in Tesla cars.
“AM radio stations are accessible through our internet radio service in
Model X. Because AM audio quality can be very poor, we offer internet radio
to give our customers considerably better sound quality and reception
coverage,” a Tesla spokesperson told me over email. Apparently, finding the
stations isn’t always easy though; there’s a Tesla forum devoted to figuring
out how to locate AM stations on the Model X.
At this point you may be asking, who cares? Isn’t AM radio a dinosaur
technology with one leg in the grave? Does anyone even listen to it? The
answer is yes: about 3 million people listen to it every day, and five of
the ten most popular radio stations in the US are AM radio. “This narrative
that somehow AM radio is dying is silly,” Dennis Wharton, communications
executive at the National Association of Broadcasters, told me.
Despite the higher sound quality of the FM band and the ascent of satellite
and internet radio, the medium of FDR’s fireside chats and Rush Limbaugh is
still cemented in American culture. AM signals can travel further distances,
making it popular for talk radio and local programs like weather and traffic
reports or emergency response information. It’s also more affordable to get
on, so is home to lots of niche stations like foreign language radio,
college radio, or religious programs. “It’s a haven for minority radio
stations as well—particularly Latino and Hispanic radio has moved a lot to
AM radio in recent years,” said Wharton. Not to mention some major sports
franchises still broadcast games, sometimes exclusively, on legacy AM
stations that have been around forever and have fiercely loyal listeners.
The National Association of Broadcasters (NAB) is asking BMW to reconsider
its decision to drop AM radio, and NAB’s California branch has teamed up
with engineers to devise a solutions to the static problem. A group of
engineers in Germany are also working on a prototype for minimizing
interference by shielding the engine’s cabling and insulating the motor, at
a price point that’s affordable for automakers.
Cars and radio have always been inextricably linked: about 90 percent of
people listen to traditional radio over the airwaves (more than use the
internet), and 40 percent of that listening happens in the car. So it’s
worth raising an eyebrow if electric cars are zooming toward the future and
leaving a historical technology behind.
[© 2016 Vice Media]
http://radioink.com/2016/02/08/bmw-listeners-want-their-am-radio-back/
BMW Owners Want Their AM Radio Back
February 8, 2016
[image / BMWBlog
http://strpubradio.wpengine.netdna-cdn.com/wp-content/uploads/sites/2/2016/02/BMW.jpg
(dash)
]
And some are willing to hack AM radio’s back into their vehicles, a clear
sign listeners want radio to remain front and center in the console. You may
recall that BMW was the first auto company to ditch AM radio in its i3
electric vehicle. Well, that has apparently is causing problems with the
owners of those vehicles.
The reason BMW dropped AM was interference from the electric drivetrain of
the car blocking out the AM signal, making it fuzzy and choppy. According to
BMWBlog those that own the vehicle have started blogs and gotten on forums
to complain about AM radio missing and some have even tried to hack AM radio
back into their cars.
The blog says, “due to AM radio’s loyal following, many automakers, BMW
included, are looking for a way to reduce and eliminate the interference
that comes from electric vehicles. If automakers can shield the wiring, and
possibly even the electric motor, then the interference could stop.”
[© Streamline Publishing]
For EVLN EV-newswire posts use:
http://evdl.org/evln/
{brucedp.150m.com}
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View this message in context:
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Sent from the Electric Vehicle Discussion List mailing list archive at
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