Broadcast

 

 

BBP Signal Settings. All settings shown here can be changed on the fly. Above is the Signal Settings window with MPX output enabled (FM Radio).

 

 

 Signal Settings window with MPX output disabled (Web, Digital or AM radio).

 

Bypass

Bypasses the front-end (dynamics processing). Pre-emphasis and clipper back-end are still active.

 

Pre-Emphasis (drop-down)

Pre-Emphasis is a progressive high frequency boost, used for FM and AM radio as a noise suppression technique.
Every radio receiver has de-emphasis built in.

Breakaway also uses Pre-Emphasis and De-Emphasis to avoid audible bit rate reduction induced clipping distortion.

Available options:

  • 75us - a very severe high-frequency boost applicable to the following broadcast scenarios:
    FM Radio in North and South America and parts of Asia
    AM Radio worldwide
    75us translates to a 3dB boost at 2.1 kHz, growing to 17.6dB at 16 kHz!
  • 50us - a less severe high frequency boost applicable to the following broadcast scenarios:
    FM Radio in Europe, Australia, Russia
    AM Radio worldwide
    50us translates to a 3dB boost at 3.2 kHz, growing to 14.2dB at 16kHz.
  • 25us - a relatively light high frequency boost suitable for low and medium bitrate encoding, when used in combination with de-emphasis.
    This serves to "pull" the high frequencies away from the edges of the wave form, where they would cause clipping distortion in decoders.
    25us translates to a 3dB boost at 6.4 kHz, growing to 8.6dB at 16kHz.
  • 15us - a very light high frequency boost suitable for high bitrate encoding (192kbps and above), when used in combination with de-emphasis.
    15us translates to a 3dB boost at 10.6 kHz, growing to just 5.2dB at 16kHz.

Even though pre-emphasis for FM is standardized, it is not set in stone. Frequency response tends to be arbitrary anyway once multiband compression is involved.
Thus, if you desire a more mellow sound, it's perfectly acceptable to use 50us in North America, or maybe even 25us in Europe. Likewise, if you desire an extremely edgy sound, you might want to use 75us in Europe.

 

L/R De-emphasis (on/off)

This option turn de-emphasis on or off. The de-emphasis curve will correspond to the selected Pre-emphasis, yielding flat frequency response -- the only difference is in the amount of high frequency headroom.

If you want to use an external stereo encoder, L/R de-emphasis must remain off, and pre-emphasis in the stereo encoder must be also be OFF. De-emphasis and re-pre-emphasis will result in either severe overmodulation, or as much as 6dB loudness loss.

If you want to listen to the output directly, this option should be ON, or the extreme high frequency boost may fry both your speakers and your ears. (Remember, Speakers can be replaced -- body parts, not so easily).

For L/R output to a streaming encoder, this option should be ON.

This option does not affect the MPX output or the DSP encoder output.

 

High pass filter (drop-down)

Phase linear brick wall high pass filter, to filter out subsonic frequencies without affecting phase response / tilt. 

Available options:

  • Off
  • 30 Hz - recommended for FM and digital radio
  • 45 Hz - recommended for FM and digital radio
  • 60 Hz - recommended for AM music radio
  • 80 Hz - recommended for AM talk radio
  • 100 Hz - recommended for AM talk radio
  • 120 Hz - recommended for AM talk radio

Extremely sharp filters - the 30Hz option is flat down to 30 Hz, and already has 40dB attenuation at 25 Hz!

 

Bandwidth (drop-down)

Controls the high frequency bandwidth. Every bandwidth setting yields impeccable peak and spectrum control.

Available options:

  • 16.0 kHz - recommended for FM radio
  • 15.5 kHz
  • 15.0 kHz
  • 14.0 kHz
  • 13.0 kHz
  • 12.0 kHz
  • 11.0 kHz
  • 10.0 kHz - recommended for wide band AM radio
  • 9.0 kHz
  • 7.5 kHz
  • 5.0 kHz - recommended for narrow band AM radio

For low bitrate streaming it is very important to match the output bandwidth to the encoder's available audio bandwidth, as any downstream filtering will result in severe overshoots and clipping distortion.

We strongly recommend 16.0 kHz for FM radio as the sharp brick wall filtering yields 60dB +/- 3 kHz of pilot protection even at this extended bandwidth setting. 

 

Phase Scrambler (on/off)

The phase scrambler will redistribute the high frequency harmonics of sharp instruments such as saxophone, certain voices, and certain sharp electronic sounds, for vastly improved high frequency headroom and lower IM distortion.

Recommended setting: ON

 

Stereo (on/off)

This setting not only controls pilot on/off for FM MPX encoding,  but also sums the audio to mono before the front-end, and substantially lowers CPU use.

If your broadcasting in mono, we strongly recommend turning this option OFF.

 

ITU SM.1268 Limiter (on/off)

ITU-R SM.1268-1 is the official name of the standard which defines what the Dutch like to call "Stokkemasker". It is a standard used for FM broadcasting in the Netherlands, which limits the maximum spectral footprint of the FM carrier. By using this specially designed minimal impact L-R limiter, compliance is virtually guaranteed - provided that you calibrate deviation to +/- 75 kHz including RDS. This limiter causes very minimal impact to the stereo image -- it does just enough to keep your signal within the mask. It operates in the L/R domain, and thus works equally well with external stereo encoders!

 

Test Tones (drop-down)

BBP features a comprehensive line-up tone generator to aid in calibrating for FM and calibrating for AM.

Available options:

  • 400 Hz - standard sine wave lineup tone
  • 1000 Hz - standard sine wave lineup tone
  • 60 Hz Square wave - for calibrating Output Tilt
  • 1000 Hz Square wave - not particularly square due to bandwidth constraints, but useful for adjusting HF EQ for AM broadcasting.
  • QuickSweep - 1000 to 56000hz sweep with a boundary click roughly 60 times per second. Useful for adjusting HF EQ for FM broadcasting.
  • 57000.0 Hz - high frequency sine wave - useful for verifying FM MPX output bandwidth with a modulation monitor
  • 31187.6 Hz - Bessel-function 1st Null, for accurately adjusting +/- 75 kHz deviation with a spectrum analyzer
  • 13586.7 Hz - Bessel-function 2nd Null, for accurately adjusting +/- 75 kHz deviation with a spectrum analyzer
  • 8667.4 Hz - Bessel-function 3rd Null, for accurately adjusting +/- 75 kHz deviation with a spectrum analyzer
  • 60 Hz Sawtooth - For verifying linearity of an AM transmitter with a single channel oscilloscope
  • 60 Hz Sawtooth + Detent - For verifying linearity of an AM transmitter with a single channel oscilloscope
  • 400 Hz Sawtooth - For verifying linearity of an AM transmitter with a single channel oscilloscope

 

L/R Ref Level (slider)

100% output reference level. Make sure to leave enough headroom to allow for Tilt and EQ compensation!

 

MPX Ref Level (slider)

100% output reference level. Make sure to leave enough headroom to allow for Tilt and EQ compensation!

 

L/R PEQ (sliders)

Single-band phase linear parametric EQ to compensate for high frequency rolloff in sound card dacs, STLs and transmitters. Useful by using the QuickSweep line-up tone and adjusting while looking at a hardware oscilloscope connected in parallel with the exciter.

  • Gain: Center gain of the parametric EQ. Range: -12 to +12dB in 0.01dB steps.
  • Center Frequency: 20 to 20000hz
  • Bandwidth: 0.05 to 10 octaves

 

MPX PEQ (sliders)

Single-band phase linear parametric EQ to compensate for high frequency rolloff in sound card dacs, STLs and transmitters. Useful by using the QuickSweep line-up tone and adjusting while looking at a hardware oscilloscope connected in parallel with the exciter.

  • Gain: Center gain of the parametric EQ. Range: -12 to +12dB in 0.01dB steps.
  • Center Frequency: 20 to 80000hz
  • Bandwidth: 0.05 to 10 octaves

  

Pilot Level (slider)

Adjusts FM MPX Pilot Level (0 to 12%)

 

Tilt (L/R out) (slider)

Adjusts output tilt compensation. For FM, adjust with Test Tone set to 60 Hz square, while watching a DC coupled hardware oscilloscope connected in parallel with the stereo generator. 
For AM, adjust with the Test Tone set to 60 Hz square, while watching a hardware oscilloscope connected to the RF sampling loop of the AM transmitter.

 

Tilt (MPX out) (slider)

Adjusts output tilt compensation for the FM Stereo MPX composite signal. Adjust with Test Tone set to 60 Hz square, while watching a DC coupled hardware oscilloscope connected in parallel with the exciter.

 

External Pilot (indicator)

Displays the state externally generated 19 kHz pilot tone into the RDS / Pilot input. If using an external RDS encoder, external pilot should be used.

If the pilot suddenly disappears, Breakaway will crossfade to internal pilot. No clicks or glitches are generated during this transition. Breakaway stays on the air in full stereo. 

 

RDS level (indicator)

Displays the current outgoing RDS level, after RDS Gain is applied.

 

RDS Gain (slider)

Allows gain adjustment of the incoming RDS signal, to achieve the desired level. 

 

Asymmetry (AM) (slider)

For AM broadcasting only. Allows you to adjust clipping asymmetry, from 0 to 50%, that is, up to 100% negative, 150% positive, or 70% negative, 105% positive (for C-QUAM stereo).
Asymmetry values higher than 20% are not recommended, as asymmetry can cause severe IM distortion on difficult instruments like Saxophone.

 

Stereo Mode (drop-down)

Selects L/R or Mid-side (sum-difference) matrix.

Available options:

  • Left/Right - normal operating mode, for FM, AM Mono, Web and Digital broadcasting. Processing is discrete Left / Right.
  • M/S (L/R out) - for AM stereo. Processing is discrete Mid / Side, but output is dematrixed to Left / Right.
  • Mid/Side - for AM stereo. Processing is discrete Mid/Side, and so is the output.

Warning: This option must be set to Left/Right for FM, Web and Digital broadcasting. Any other setting results in a 6dB loudness loss.

 

Invert Input (on/off)

Allows inverting the input, to match phase with studio microphones. Useful if using asymmetrical clipping.

 

Invert Output (on/off)

Allows inverting the ouput, to match phase with the AM transmitter. Useful if using asymmetrical clipping.

 

Effect Plug-ins

  • Edit - opens the plug-in selection window, where you can select up to 9 Winamp DSP effect plug-ins (such as reverb, stereo enhancers)
  • Reload - loads or reloads the plug-ins. Press this button after selecting plug-ins in the Edit window.
  • Config - opens the configuration window for all loaded plug-ins.

 

Encoder Plug-ins

  • Edit - opens the plug-in selection window, where you can select up to 9 Winamp DSP encoder plug-ins (such as shoutcast)
  • Reload - loads or reloads the plug-ins. Press this button after selecting plug-ins in the Edit window.
  • Config - opens the configuration window for all loaded plug-ins.