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Stereo Tool 7.83 - Help - AM Transmitter

AM Transmitter section

Settings for AM transmitters.

AM Transmitter panel

AM asymmetry settings.

AM Pre-emphasis panel

NRSC AM pre-emphasis (US/ITU region 2 only).

  • NRSC Modified 75 Ás AM Standard Preemphasis (US)
    Enables NRSC AM pre-emphasis.

  • Pre-emphasize output
    Output to sound card is pre-emhpasized.

    If you do not enable this button, the output is de-emphasized before it is sent to the sound card. Without this button the sound equals what a listener will hear on an AM radio.

AM Stereo panel

Controls AM mono or stereo output.

  • AM Downmix to mono
    Downmix audio to mono for mono AM transmitters.

    The downmixing is more sophisticated than traditional downmixing, because any issues caused by phase differences between the channels (phase cancellation) are solved. So to get the best sound, it's better to feed Stereo Tool with stereo input and use this downmix switch than to feed Stereo Tool with mono input.

  • AM Stereo (C-QUAM) clipping/limiting
    C-QUAM AM Stereo compliant clipping and limiting.

    The output signal is clipped and limited such that it complies fully to Motorola C-QUAM AM Stereo regulations and guidelines.

    Please note that when broadcasting in AM Stereo using C-QUAM, the bandwidth of the signal increases slightly. There will be some signal above 10 kHz present in the signal that comes out of a stereo AM transmitter. This is normal for C-QUAM, but when switching form mono to stereo it's important to make sure that you're not causing problems to other stations.

AM asymmetry panel

Asymmetrical clipping and limiting for AM stations.

AM stations can broadcast an asymmetrical signal - peaks to the top may be higher than peaks to the bottom (which would cause the carrier to disappear). Local regulations (amount of asymmetry allowed) may vary.

The effect of asymmetry on the audio signal is not very big, and some older transmitters might not be able to handle it very well. Use with care.

  • AM asymmetric limiting and clipping
    Enables asymmetrical limiting and clipping for AM stations.

  • Allow bigger peaks to
    The direction in which higher peaks are allowed.

    This depends on how the transmitter is connected to the sound card. Tests are probably needed to determine the correct setting.

  • Asymmetry Strength
    How asymmetrical the sound may be.

    The allowed value here depends on your local legislation. Values upto 200% are supported, but usually not allowed.

    Note: Opposed to other uses, when you increase this level, you need to lower the settings of Post amplifier to allow for the extra headroom. This is a workaround for now.

  • Use asymmetry settings also for FM (Experimental)
    EXPERIMENTAL: Enables asymmetrical clipping and limiting for FM stations (!)

    If 2 stations from the same owner are located close to another and very close in frequency, for example only 100 or 200 kHz apart, then it might improve the reception if for both frequencies the bandwidth towards the other frequency can be reduced.

    This is currently available for testing only and it does not work if the composite clipper for FM is enabled.
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