Talk:Pilot signal

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Proposed merger from Pilottone

The Pilottone article is uncategorised and has only two links into it. Merger this way round looks logical to me, though I'm not an expert. --Mereda 13:15, 23 August 2006 (UTC)[reply]

I agree it doesn't have many links to it, but "pilottone" refers almost exclusively to a pilot tone recorded on an audio tape, strictly for the purpose of sychronization, while pilot tone, from its article, appears to refer to a much broader concept, and says nothing about the use of pilot tones in recording; it pertains completely to pilot tones in broadcast or radio. If I were interested in pilottone from the Nagra article and came to the pilot tone article, I might find it confusing, since the pilot tone article is overly-general with regard to pilottone on Nagras. $0.02 Iluvcapra 03:44, 23 September 2006 (UTC)[reply]

Inaccurate Sentence

This sentence is inaccurate: "In FM stereo broadcasting, a pilot tone of 19 kHz indicates that there is stereophonic information at 38 kHz (19×2, the second harmonic of the pilot)." It should read as follows: "In FM stereo broadcasting, a pilot tone of 19 kHz in the demodulated audio signal indicates that stereophonic information is included as a double-sideband supressed carrier signal centred at 38 kHz, the supressed second harmonic of the pilot." — Preceding unsigned comment added by 82.32.48.177 (talk) 11:13, 26 April 2012 (UTC)[reply]

Clarification needed

Phrases like "pilot tone of 19 kHz" confuse me, as it is not clear where this tone is in relation to the main frequency-modulated signal. I see at least two possibilities, but the article does not distinguish between them. First, it is possible that an FM signal is a simple frequency modulation, relative to a carrier frequency that is only transmitted when silence is being transmitted. If this is the case, then the pilot tone of 19 kHz would appear only after the main signal is demodulated to produce the baseband signal. That baseband signal might contain the pilot tone, stereo information, RBDS, and other data.

The second possibility is that a broadcast FM signal is some kind of composite of the main frequency modulated signal plus additional carriers or subcarriers which are modulated to contain additional information, such as the stereo information and the pilot tone of 19 kHz.

If no one wants to find reliable sources for explaining FM signals better, or if no such sources exist, fine. Then I would settle for someone knowledgeable adding the information based on their personal knowledge. David Spector (talk) 16:35, 3 August 2013 (UTC)[reply]

The whole sum of (L+R), pilot, stereo subcarrier, and any SCA subcarriers frequency modulates the main carrier. In AM, you could add sidebands to the carrier, as things are linear, but they are not for FM. You can't make FM by adding up separately modulated signals. Figuring out bandwidth is a little more complicated. In theory, the transmitted FM signal has infinite bandwidth with any modulation. In practice, it is close enough for actual use. Broadcast FM uses 75kHz deviation in a 200kHz wide (+/- 100kHz) channel. Audio is limited to about 15kHz to keep away from the pilot on both sides, so the stereo (DSB-SC) subcarrier is about 38kHz +/- 15kHz, so up to 53kHz. Then the (lower bandwidth) FM SCA subcarrier is added, at lower amplitude. SCA is an FM subcarrier to the FM transmitter. Double FM. I believe this is well described in the appropriate article on FM broadcasting. Gah4 (talk) 22:18, 17 April 2021 (UTC)[reply]