Connect with us

FM Stereo

Discussion in 'General Electronics Discussion' started by dm99, Jan 9, 2013.

Scroll to continue with content
  1. dm99

    dm99

    26
    0
    Oct 29, 2012
    How does "FM Stereo" work? If you're listening to a station transmitting in stereo with a mono radio are you missing one of the channels?
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
  3. Merlin3189

    Merlin3189

    250
    69
    Aug 4, 2011
    They thought about that when they designed it. So the two signals they transmit are the sum of the L & R channels and the difference of the L & R channels.
    A mono reciever ignores the latter and just hears the sum - the two channels added together.
    A stereo rcvr adds the two signals (L+R and L-R) to give just the left channel, and it subtracts the two signals (L-R subtracted from L+R) to give just the right channel.
    I suppose to be algebraically correct, one ought perhaps to say,
    L = 0.5 ( (L+R) + (L-R) )
    R = 0.5 ( (L+R) - (L-R) )

    The first signal, L+R, was modulated in the normal way, so thats what the mono receiver picks up. So no change was needed in existing receivers.
    The second signal (L-R) was modulated onto a sub-carrier at a frequency outside the normal mono pass band, so that mono receivers ignored it. A stereo receiver had a wider passband and processed both signals.
     
    Last edited: Jan 10, 2013
  4. quantumtangles

    quantumtangles

    152
    3
    Dec 19, 2012
    Interesting. If you wanted to build a stereo FM circuit on a breadboard, what would be the most basic FM stereo circuit you could build in terms of the minimum number of basic components + an IC?
     
  5. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
  6. davenn

    davenn Moderator

    13,672
    1,891
    Sep 5, 2009
    breadboarding anything RF particularly above 50MHz and in this case the 88-108MHz FM broadcast band is a really really bad idea
    The circuit will most likely oscillate ... ie will be unstable
    even building 50MHz and up on veroboard will be problematic for similar reasons

    its all because of stray inductance and capacitance between adjecent strips

    As I said really not a good idea ;)

    Dave
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-