Talk:AM broadcasting

Short wave

i thought short wave went up to 29,999 kHz? tahstw hat it does on my sw radio. -fonzy

You could be right. My Sony only goes up to 26100 kHz, though, which is where I got the figure from. Feel free. GrahamN 19:52 Jan 23, 2003 (UTC)

I have a digital one(not DAB, digital dial) i think the MW one is wrng too. as it goes up to 17,010 khz on mine, then sw starts on 17,011 starts. - i dont really know enough about radio btu i am shore that sw goes up to 30 Mhz. -fonzy

The current American AM band extends from 540 to 1700KHz wheras the official European MW band is from 531 to 1602 KHz also in both cases there are stations operating "just" outside the official band so the defacto band goes from 520 to around 1720 KHz (confusingly some older European radios mark dial position in metres instead) Officially "Shortwave" (HF) covers the range 3 to 30 Megahertz however there is no (legal) shortwave BROADCASTING above 26.1 MHz (remember the radio spectrum is used for many other things besides broadcasting) also Most people consider the bands between the top end of the meduimwave band and 3 MHz to be "shortwave" even if they are not officially classed as such. Most "Shortwave" radios only cover the most popular broadcast bands (some only cover the "49 Metre"/6 MHz broadcast band) Some treat Shortwave as a single "band" while some (particualrly analouge tuned) radios split it up into smaller ranges (often marked "SW1" "SW2)" etc to make tuning easier.

Does this help? It's a bit surprising that the definitions seem so vague. GrahamN 20:16 Jan 23, 2003 (UTC)

All thsi conflicting data hurts my head :-s, we need someone who really is an expert on this. -fonzy

How about if we round the numbers off and qualify them with "approximately"? GrahamN

Yes do taht for now might be good to put an HTML comment on the paeg saying if you deffently know what it should be please say. -fonzy

---

The trad. modulation used for telegraphy (carrier either on or off) is called CW. Although the amplitude is modulated per se (0 or 100%), the term AM is never used for this. I have thus removed the following sentence:

... for radio telegraph communication early in the 20th century ...

Okay. I think we really could use an article on radio telegraphy, are you up to it? I had thought that it was on AM frequencies; I remember hearing lots of Morse Code on medium and shortwave as late as the mid 1970s, was that something different from what is ususally called radio telegraph? -- Infrogmation

The point is it is not "AM" (as in amplitude modulation), so it is not "AM radio". Even though it happened to occur in bands also used for AM. My suggestion is that the term "AM radio" should mean "public broadcasting using amplitude modulation", while "AM" should mean "amplitude modulation" in the more technical meaning. Morse using CW is neither. Sorry, I don't know too much about radio telegraphy history and such, so all I can contribute would be a silly stub. -- Egil 18:14 Feb 4, 2003 (UTC)

Not all morse telegraphy is "CW" Some is "MCW" "FSK" etc Actually even "CW" is a bit of a misnomor. It should really be termed "ICW" (interrupted continous wave)

frequencies

The term "commercial radio broadcasting" in this context is rather confusing (Long wave is used for commercial radio broadcasting in Europe, Africa, Asia,.....) Since the majority of Longwave and Shortwave (as well as much Mediumwave) broadcasting is infact NON-commercial. Also Long wave is NOT used for broadcasting in "Australasia". In the 1930's when the ABC was being established in Australia t was originally proposed that LW should be used but a for various reasons mix of MW and SW (and later FM etc) was decided upon instead.

Globalize

Tagged with globalize/north america for these reasons:

• The first licensed commercial radio services began on AM in the 1920s. XWA of Montreal, Quebec (later CFCF) was the first commercial broadcaster in the world, with regular broadcasts commencing on May 20, 1920. The first licensed American radio station was started by Frank Conrad, KDKA in Pittsburgh, Pennsylvania. -- No mention of any other countries.
• In North American broadcasting practice, transmitter power input to the antenna for commercial AM stations ranges from about 250 watts to 50,000 watts. (rest of paragraph omitted to save space). -- No mention of the broadcasting practices for any other region.
• As a result, many broadcast stations are required as a condition of license to reduce their broadcasting power significantly (or use directional antennas) after sunset, or even to suspend broadcasting entirely during nighttime hours. -- Not clear from the article if this is specifically North American practice or is found everywhere.
• In the United States and Canada, some AM radio stations are granted clear channel status... -- No mention of the practices in any other country.
• The hobby of listening to long distance signals is known as DX or DX'ing, from an old telegraph abbreviation for "distance". Several non-profit hobbyist clubs are devoted exclusively to DXing the AM broadcast band, including the National Radio Club and International Radio Club of America. -- No mention of this hobby in other regions, but is instead stated as if this is the terminology everywhere.
• AM radio is broadcast on several frequency bands. The allocation of these bands is governed by the ITU's Radio Regulations and, on the national level, by each country's telecommunications administration (the FCC in the U.S., for example) subject to international agreements. -- Example is USA only. No other examples for any other country given.
• However, in the late 1960s and 1970s, top 40 rock and roll stations in the US and Canada such as WABC and CHUM transmitted highly processed and extended audio to 11 kHz, successfully attracting huge audiences. In the UK during the 1980s, BBC Radio 4 (a largely speech channel) had an FM location, whereas BBC Radio 1, a music channel, was confined to AM broadcasts over much of the UK. Frequency response is typically 40 Hz–5 kHz with a 50 dB S/N ratio. -- North American perspective again. Also notable for one of the very few places in the whole article that even mentions any broadcasting practice outside of North America.
• The limitation on AM fidelity comes from current receiver design. Moreover, to fit more transmitters on the AM broadcast band, in the United States maximum transmitted audio bandwidth is limited to 10 kHz by an NRSC standard adopted by the FCC, resulting in a channel occupied bandwidth of 20 kHz. -- USA perspective, other viewpoints absent.
• In the United States, iBiquity's proprietary HD Radio has been adopted and approved by the FCC for medium wave transmissions, while Digital Radio Mondiale is a more open effort often used on the shortwave bands, and can be used alongside many AM broadcasts. -- No mention of the practices elsewhere, yet again.
• While FM radio can also be received by cable, AM radio generally cannot, although an AM station can be converted into an FM cable signal. In Canada, cable operators that offer FM cable services are required by the CRTC to distribute all locally available AM stations in this manner. In Switzerland a system known as "wire broadcasting" transmits AM signals over telephone lines in the longwave band. North american perspective. Also notable as one of the few places that mentions a country outside North America.
• Some microbroadcasters and pirate radio broadcasters, especially those in the United States under the FCC's Part 15 rules, broadcast on AM to achieve greater range than is possible on the FM band. No mention of the practice elsewhere.

Virtually every paragraph discusses the USA and/or Canada in depth, but only in a few places in the article are other countries mentioned by name. The article needs a substantial overhaul if it is to be more representative of the global audience of Wikipedia, per MOS. -- B.D.Mills  (T, C) 01:00, 13 November 2008 (UTC)

LONG WAVE USA

I live in the USA. Right now I hear radio stations broadcasting on long wave AM, for example 180 KHZ. Surely part of this article is in error. (EnochBethany (talk) 18:52, 11 September 2012 (UTC))

What stations do you hear? Have you been able to hear their names? CodeCat (talk) 21:46, 11 September 2012 (UTC)

Usual broadcast AM in the US is from 520kHz to 1600kHz. (or maybe 530kHz to 1700kHz.) There are other bands allocated for other uses, some for amateur (HAM) radio. Gah4 (talk) 18:00, 14 February 2017 (UTC)

Stereo

An encyclopedia would certainly mention the kind of stereo already specified and in current enforcement by the U.S. Government. This is "AM Analog Stereo", which has no connection to the AM digital stereo already covered in the article. And to address the international nature of Wikipedia articles, most countries have implemented "AM Analog Stereo" in a small minority of their stations as well. What should be noted in the article is that the kind of AM Stereo on the books is virtually the same for both the U.S. and practically all other countries. That kind of AM Analog Stereo is "C-QUAM". Another easily sourced information on the difference between "AM Analog Stereo" and "AM Digital Stereo", is that the "C-QUAM" flavor of "AM Analog Stereo", besides being the only flavor of AM Analog Stereo authorized by governments around the world, also has no licensing fees, unlike the popular AM Digital Stereo. Ohgddfp (talk) 11:55, 15 August 2013 (UTC)

The article does say: "Stereo transmissions are possible (see AM stereo), ...". And the link points to an article about analog stereo systems. CodeCat (talk) 12:01, 15 August 2013 (UTC)

Yes, I see that. The problem is that the article mentions "Stereo" and has that link. But in the same sentence, "digital" is visible BEFORE following the link, but "analog" is discoverable only AFTER following the link. Most readers will not follow the link, and therefore get the false idea that stereo is a digital technology and not an analog technology. Especially since readers are conditioned to believe that all digital audio is stereo. Yes, it's the reader's "fault" for not following the link. But a balanced report on "stereo" should not require the reader to follow a link for one kind of stereo but not have to follow a link for the other kind of stereo. This is what false ideas in readers heads are made of. So in the "stereo" section, mentioning neither analog nor digital would be an improvement, with the link giving the details. An alternative to prevent that kind of confusion would be to mention both analog and digital in the main article. Ohgddfp (talk) 12:58, 15 August 2013 (UTC)

I've made some changes. Is this better? CodeCat (talk) 13:58, 15 August 2013 (UTC)

It's indeed better. Now I'm wondering if this is even better, "While uncommon, AM stereo transmissions are possible using a variety of means, both digital and analog." I guess it's not strictly needed. Are those extra words worth it? I dunno. I would add them myself, but the paragraph now as you have it is also logical without them. Ohgddfp (talk) 15:59, 29 November 2013 (UTC)

I vote for the extra wording. While the government may allow for it, I have never seen an AM stereo receiver. You are lucky to get one that is even high-fidelity, even in an otherwise high-fidelity system. Without demand of listeners, there is no reason for broadcasters to transmit it. I could be wrong, maybe many are. Gah4 (talk) 18:03, 14 February 2017 (UTC)

heterodyning: "the principle on which AM modulation is based"

Are there any radio engineers reading this who think that this statement is misleading? In my view "heterodyning", and the selected sources, are being misused in this context. Sum and difference frequencies (sidebands) are generated when a signal is amplitude modulated, but that is more of a consequential effect of the amplitude modulation than a principle by which to amplitude modulate, as this statement would suggest. Wildbear (talk) 00:15, 22 September 2013 (UTC)

Heterodyning, the mixing of two frequencies f₁ and f₂ in a nonlinear device to get sum and difference frequencies, which Fessenden discovered, is the principle behind AM modulation, demodulation, frequency conversion, superheterodyne reception, frequency multiplication, and a number of other things. A good deal of telecommunication theory is based on it. The formula is:

$\cos(2\pi f_{1}t)\cos(2\pi f_{2}t)={\frac {1}{2}}\cos[2\pi (f_{1}+f_{2})t]+{\frac {1}{2}}\cos[2\pi (f_{1}-f_{2})t]\,$

If f₁ is a radio carrier and f₂ is a baseband modulation frequency, you get amplitude modulation

If f₁ is a sideband of a modulated signal and f₂ is the carrier, and you filter out the difference f₂ - f₁, you get demodulation.

If f₁ is a received radio signal, f₂ is a local oscillator signal, and you filter out the difference f₂ - f₁, you get an intermediate frequency (IF) for superheterodyne reception.

Etc. --Chetvorno^TALK 01:39, 22 September 2013 (UTC)

Mathematically, the same formula applies to the various forms of signal processing. Differing semantics have been in use since Fessenden's time, to distinguish the type of processing being applied by the circuitry. Quoting a previous discussion on the matter:

Mixing is probably most general, as it means nonlinearly combining two signals (in audio it means linearly, but that's different). AM modulating is bilinear mixing a baseband signal with a carrier oscillator signal. Heterodyning is mixing an RF signal with a local oscillator signal of a frequency different from the RF carrier frequency. Homodyning is mixing an RF signal with a local oscillator signal of same frequency as the RF.

— Dicklyon, Talk:Amplitude_modulation#The_idea_of_Heterodyning

If you were to change the text to read: "He also discovered the principle on which AM modulation is based, bilinear mixing a baseband signal with a carrier oscillator signal", I would find it more agreeable (since this is proper terminology for the amplitude modulation process) than to state that the amplitude modulation process is based on "heterodyning" (which in common usage in the radio frequency realm, and likely in Fessenden's usage as well, implies mixing two RF signals). Ultimately, it's an issue of semantics, not mathematics. Wildbear (talk) 05:46, 22 September 2013 (UTC)

In theory, you can generate AM by directly modulating an RF signal. As the article suggests, in the early days this was done with full power RF through a carbon microphone, limited by its power handling capability. But practically, the way it is done is to take the audio signal and mix (heterodyne) it with the RF carrier (or an IF carrier). So, while I agree that it is misleading in the direct carbon microphone case, it isn't in the way transmitters have been made for many decades now, pretty much since the invention of the vacuum tube triode. Gah4 (talk) 18:10, 14 February 2017 (UTC)

"Crystal Gayle" effect

Recently an editor added this unsourced paragraph on a quirk in vacuum tubes discovered when Crystal Gayle records were played in the 1980s to the "Vacuum tubes" section. While this is interesting and entertaining, I feel in addition to not being notable enough, it is off topic for this section and this article. The "Vacuum tubes" section is about the historical introduction of vacuum tubes to radio around 1920, so a minor quirk in modern tubes does not belong here. In addition I am not sure it belongs in this article; perhaps it would be more appropriate in Vacuum tube, Triode, or Radio broadcasting --Chetvorno^TALK 23:00, 19 April 2015 (UTC)

Seems like a specific case of microphonics, which has been known for years. I would suggest that it go into that article. Microphonics is the general unintentional connection between sound waves and electronics. It isn't obvious if this is an unlucky resonance that happened to be right for Ms. Gayle. Gah4 (talk) 18:15, 14 February 2017 (UTC)

MWLIST quick and easy: Europe, Africa and Middle East

See also http://www.mwlist.org/mwlist_quick_and_easy.php 84.80.54.162 (talk) 17:32, 7 July 2016 (UTC)

AM vs. FM dominance, the time line and reasons for it.

There is a statement, with {{citation needed}}: Finally, the 10 kilohertz minimum separation between stations in the United States limits fidelity to sounds much lower than the upper limit of human hearing, and the advent of high-fidelity recording equipment has created a demand for high-fidelity radio. First, it doesn't say which part of the statement needs a citation, but the statement itself is questionable. While 20Hz to 20kHz is the common frequency range for describing audio equipment, most people's hearing drops of closer to 15kHz. The highest note on the usual piano, from Piano_key_frequencies, is 4186Hz. There isn't much music up there, though the harmonics of some notes make it sound a little nicer. The problem is more that both transmitters and receivers aren't well designed, to save on costs, to get the most out of the available bandwidth. Gah4 (talk) 18:29, 14 February 2017 (UTC)

The next paragraph seems to suggest that the FM broadcast band shift in 1946 is responsible for the delay until the 1970's of FM's dominance. That seems hard to believe. Car radios were AM only for many years, and many home and portable radios also were for many years. But for people who wanted to listen to high fidelity audio, FM broadcasting was the first choice much earlier. Some people in 1946 had useless radios, though. Gah4 (talk) 18:29, 14 February 2017 (UTC)