|WikiProject Radio||(Rated Start-class)|
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Very clever, this demonstrates that hackers have existed long before computers.
This portion of the article incorrectly states that color television signals contain red and blue color values. This is not true. NTSC, PAL, and SECAM television encodes color as chroma (position on the color wheel) and a saturation (vividness of the color varying from grey through brownish earth tones up through pure rainbow primaries). This type of color encoding is not dependant upon the mixing of specific component colors, and gives receiver manufacturers freedom to impliment color decoding an numerous possible ways. High quality sets have been built with multiple colors of phosphors in addition to red, green, and blue.
Actually, I think the reason stereo drops off before mono is that the stereo signal is AM, and the subcarrier is FM. AM is much more susceptible to inference. That problem would have been eliminated by the Crosby system. 188.8.131.52 04:56, 13 Feb 2005 (UTC)
this statement from the Subcarrier page is not correct to my knowledge >>> Note that higher frequencies drop off much more rapidly, which explains why FM stereo gets noisy at a distance, while switching to mono is still perfectly clear and easy to listen to.
a radio engineer would know this subject well (and hopefully one will post a technically correct explanation here soon)...i am not a radio engineer but i have some knowledge re this subject....fm stereo gets noisy because the stereo subcarrier signal is injected into the fm stations rf carrier at around 15khz and this somehow creates a lot of noise when the stations rf signal level is low....in mono mode the stereo subcarrier signal is ignored(or plays no role) and the result is far less noise at weak rf signal levels....i know this is a poor explanation and i hope a 'real radio engineer'/credible source will correct this soon...12/26/05
I'm not a radio engineer either, but I'm well-versed in signal analysis. I think that I can answer that "somehow". The reason that stereo is noisier than mono is that, when the stereo signal is combined with the mono signal, the noise from the stereo is signal is also added in. Imagine the typical radio-announcer situation of a mono microphone. Both the right and the left will have the same signal, so the stereo subcarrier (which is the difference between the two) will carry no signal, just noise. Guess what happens when that is added to (or subtraced from) the mono signal to recreate the right and left. 184.108.40.206 12:47, 18 October 2007 (UTC)
Interesting stuff; I think I understand what this is about, but a diagram would really be a good addition to the article.
For example, the way that TV colour is encoded; I understand the article to be saying that colour TV RF transmissions are received, demodulated, and that this gives us a "spectrum" containing the (now) unmodulated (baseband) luminance signal, as well as the colour information modulated on a subcarrier at (I assume) a position beyond the top-end of the luminance signal.
I might do something myself, but I'd definitely have it checked first. :)
Fourohfour 18:21, 8 January 2006 (UTC)
A lot of the information here regarding subcarriers of the FM band seems to be in the FM broadcasting article as well. Perhaps merge the relevant sections into that one and reference from here? 220.127.116.11 19:06, 24 July 2007 (UTC)
Hi folks! Three thoughts: [Thought 1 of 3] I updated the entry regarding the discussion of subcarrier use from it's previous version to correct the mention of "narrowband" signals (which AM broadcast is, by the way) when I believe the previous editor meant "narrow band" (which is a completely different idea in signal theory). "Narrowband" is about the flatness (relative equality) of signal coherence over an arbitrary bandwidth; "narrow bandwidth" is a subjective (relative) concept of how high (and how low if we're thinking of a passband) a modulated frequency can be on a given signal of an arbitrary bandwidth. A "narrowband" signal can be advantageous for meaningful subcarriers given the "narrowband" signal isn't constrained to a "narrow band". [Thought 2 of 3] Technically speaking, you can put a subcarrier into an AM signal, since a carrier is basically a tone (if you think of it in an audio paradigm), but there's no way to make the continuous carrier inaudible without notch-filtering the AF-stage on a standard AM-broadcast radio--the entire AM signal bandwidth can be used for audio. You'd hear the subcarrier as a tone getting deterministically louder and quieter (if AM), wavering in pitch (if FM), or rapidly beeping/buzzing (if PWM). [Thought 3 of 3] I kept thinking while I was typing "Why are we talking about AM radio in an FM radio section of this article? Oh well, just fix this section for now--the AM thing was already there and that's what got me editing in the first place." Ed 06:56, 8 September 2007 (UTC)
I edited the introduction to this article to address some issues and to make it more concise. There are issues in the opening sentence where there is confusion between the subcarrier and the sidebands of the subcarrier. The second sentence has been simplified and elaborated upon.