Why are FM radio tuner cards so ubiquitous but tuner cards that support AM virtually or completely non-existent? The Microsoft Zune has a radio tuner built in but it is FM only. Other radio devices that interface to the computer all seem to be FM only. Why don’t radio devices that connect to the computer support AM?
Could be…just COULD be, that some countries space stations along the AM band in 9kh intervals, and some space at 10kh intervals. Which means in this time of global markets and distribution, that no single size could fit all.
Having said that, electricity standards vary, and that doesn’t stop manufacturers.
OK, I’m out of ideas now…
M
The audio signal for television (in North America at least) uses FM, which is why one may be able to pick up the audio from a local TV channel 6 near the lower end of a radio’s FM band, around 88 MHz. As a result, televisions and TV cards for computers already need an FM tuning chip, so adding FM radio capability to a TV card is a breeze. Producing a cheap FM radio-only card means just leaving off the TV video tuner. Since AM radio encodes less information (and quality) in its signal, it’s easier to receive over broadband internet and I’ll bet this cuts into potential AM tuner card sales, to the point where no (or few) manufacturers bother to make them.
AM means Amplitude Modulation, which basically means that they vary the “loudness” of a radio wave to encode the audio signal on it. One characteristic of AM is that any noise that gets into the signal on the same frequency also adds to the “loudness” of the signal, and once the noise is mixed in there you can’t get it back out. Computers are a huge generator of electrical noise, so much so that back in the old days of the Apple II computer, some folks figured out how to play music on nearby AM radios just by toggling I/O lines at a particular frequency. In the engineering building where I went to college, we used to call AM radios “computer detectors” because you could walk down the hallway and tell which rooms had computers running and which ones didn’t just because of how much noise they created on the AM band. Computers are electrically quieter than they used to be, but they still generate a lot of electrical noise.
FM radio on the other hand works by varying the frequency back and forth to encode the audio signal. When the receiver decodes the signal, it locks onto the loudest signal and tracks its frequency. As long as the noise generated by the computer is quieter than the radio signal you are trying to receive, the noise gets completely ignored.
So, basically, if you tried to make an AM radio receiver connected to a computer it would have this annoying wrrshhhhhhgrssshhhh type sound constantly in the background which would be really annoying to listen to.
AM also isn’t very popular. There was talk back in the late 80’s and early 90’s about doing something to revive it, because at that time AM was almost a completely dead radio band. Some cars in that era were produced that didn’t even have AM on their radios. Then, talk radio took off and became popular, the AM band wasn’t quite dead, and all of the talk about changing the AM band to something else slowly went away. AM still isn’t very popular compared to FM, though.
This is probably the main reason. There simply wouldn’t be much interest in an AM tuner.
Tuner cards that cover a very wide frequency range, including AM broadcast frequencies, are available, but they’re marketed to ham radio operators and shortwave radio enthusiasts.
This is a nice unit: WiNRADiO WR-G305i Receiver
Covers 9 kHz to 1800 MHz. You can get it here: http://www.grove-ent.com/G305IPD.html for $619.95 USD.
There is the radioSHARK2. It’s USB based and seems cheap enough and also comes with software that allows you to record while you’re listening. Amazon only lists 2 reviews for this model however you can see the radioShark1’s reviews here.
Product Features (according to their website)
-87.5 to 108.0 MHz FM Tuning Range
-100kHz FM Frequency Steps
-50Hz - 15kHz FM Frequency Response
-530 to 1710 kHz AM Tuning Range
-10kHz or 9kHz AM Frequency Steps
AM is (or was) a good medium, but is prone to all sorts of interference from just about everything these days - stoves, washers, dryers, monitors, televisions, flourescent lights, computer power supplies, the list is endless. FM uses much more spectrum than the AM band but is not subject to the RFI problems.
Maybe, but that’s not because people don’t want the stuff that AM stations are broadcasting.
Most of the posts above have explained why the AM band is less desirable, but the fact is that the audience for talk radio and NPR conrinue to grow, while the audiences for FM music stations are shrinking dramatically. FM listnership has been affected by the advent of sattelite radio, the use of mp3 players, and other online sources like MySpace and YahooMusic. A recent book by Marc Fisher (Something in the Air) details this trend, as does his Washington Post article.
Many (most) AM stations offer streaming content through one outlet or another, and the proliferation of podcasts speaks to the popularity of their programming.
While the AM medium may be growing obsolete, it’s the commercial music FM stations and their over-researched programming that are dying.