fm/am/sirius/xm stereo or mono?

[blue93corsica 10+ year member]

just thought about this the other day, never really noticed or even thought to look into

now does the above mentioned come through in stereo or mono? never really noticed any left to right separation but then again when im listining to the radio i usually just get lost in the music and dont focus on this.

just a question i have been pondering lately

what are your views?

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[JimJ 5,000+ posts]

FM usually is broadcast in stereo, although it doesn't need to be.

AM is mono, although Motorola had a system out (C-QUAM, comparative quadrature AM, don't ask me what the acronym means //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif) that allowed true AM stereo to be broadcast. Didn't go anywhere though.

The decoding of the FM stereo signal is one reason the audio fidelity sucks, on top of near-100% compression...when in stereo mode, your receiver is looking for a 19KHz pilot tone broadcast by the transmitter in order to decode the multiplexed stereo signal...because of this, most stations use a really steep low pass filter on the audio around 15KHz. If audio was allowed to go up to 19KHz, it would interfere with decoding and you get this really nasty "chirping" sound out of the receiver.

 

[blue93corsica 10+ year member]

hmm interesting, thank you, how about the satalite companies then, although i assume that they shoud be a step up from am/fm so i would assume they would be stereo

 

[Prowler573 5,000+ posts]

Jim (thanks for taking care of those thread deletions for me, by the way) my dad had a Toyota Camry once upon a time that had an option on the OEM AM/FM/Cassette deck for stereo on AM channels.

I do not recall (since I was 13 at the time) whether it was simulated stereo or what but would it perhaps have been something related to the Motorola system you mentioned above?

 

[JimJ 5,000+ posts]

Could have been, Motorola brought it out in the late '70s, but nobody really did anything with it too much.

Satellite systems are in stereo, although I don't know how they're broadcast in detail.