Question "Noisy" FM reception on Pioneer SX 626

Discussion in 'Hi-Fi Stereo Systems & Separates' started by timinky, Oct 19, 2017.

  1. timinky

    timinky
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    Have noticed that on 626 when listening to FM radio signasl in the "FM-Auto" selector position which is the "stereo" position, reception is noisy. Signal is very strong as displayed on signal strength needle meter. Have noticed when I rotate selector knob to Mono listening position (for FM) the "noise" disappears. Maybe time for a service run? Any thoughts. All other sources that are sent from receiver (turntable, cassette, CD player) "noise" free. Thanks in advance for any input.
     
  2. JayCee

    JayCee
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    Try an attenuator on your FM aerial, reduce the signal strength and see if the noise disappears.
     
  3. Grumpsimus

    Grumpsimus
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    The 626 is a fairly old model but good for its day. On FM reception noise on stereo but not mono was normally a sign that the signal strength wasn't quite good enough and that you had to try and increase this. What aerial are you using?

    I wouldn't take much notice of the "signal strength meter", this was more of a decorative feature than a useful tool.
     
  4. Deleted member 781788

    Deleted member 781788
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    Just an observation, a lot of signal or strong signal is not the same thing as good signal.
    Check your antennae for position.
    On FM - two signals are broadcast simultaneously.
    1- the Mono signal
    2- The stereo difference between right and left.
    On stereo reception, the tuner adds this "difference" to the Mono signal to get one of the stereo channels and subtracts it from Mono to get the other channel.
    Now if the stereo signal is received with noise , the above process doubles the noise in stereo, as it is applied to the sound out of phase.
    Hence the extra noise on stereo.
    the stereo signal is on a 19kHz subcarrier, FM tuners have a sharp filter on anything above this frequency to minimise noise.
    I would say 9 out of 10 your aerial is to blame, and 1 out of 10 the filter is not working right.
     
  5. D'@ve

    D'@ve
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    I concur with the two posts above mine, it's probably a signal strength issue, whatever the meter indicates. The cabling and all connectors should be checked all the way from antenna to tuner input to eliminate connection issues and signal shorting, then the (hopefully FM band!) antenna checked for alignment to the transmitter, polarity positioning and anything metallic in its vicinity that could mess up the signal.

    If it's an indoor antenna, at least a loft one may be needed and if necessary an outdoor one. Whether or not this problem has always occurred or if it started recently may give some clues by identifying any changes in the setup, cabling or antenna position.
     
    Last edited: Oct 21, 2017

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