Crown Low Power Transmitters - Crown Broadcast
Crown Low Power Transmitters - Crown Broadcast
Crown Low Power Transmitters - Crown Broadcast
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3.3 Front Panel Bar-Dot Displays<br />
Bar-dot LEDs show audio input levels, wideband and highband audio gain control,<br />
and modulation percentage. Resolution for the gain control and modulation displays<br />
is increased over a conventional bar-graph display using dither enhancement which<br />
modulates the brightness of the LED to give the effect of a fade from dot to dot. (See<br />
section 4.7.)<br />
3.3.1 Audio Processor Input<br />
Two vertical, moving-dot displays for the left and right channels indicate the relative<br />
audio levels, in 3 dB steps, at the input of the audio processor. Under normal operating<br />
conditions, the left and right Audio Processor indicators will be active, indicating<br />
the relative audio input level after the Input Gain switches. During program pauses,<br />
the red <strong>Low</strong> LED will light.<br />
The translator configuration shows relative audio levels from the included receiver.<br />
3.3.2 Highband and Wideband Display<br />
During audio processing, the moving-dot displays indicate the amount of gain control<br />
for broadband (Wide) and pre-emphasized (High) audio.<br />
As long as program material causes activity of the Wideband green indicators, determined<br />
by the program source level and Input Gain switches, the transmitter will be<br />
fully modulated. (See section 3.4.)<br />
The Wideband indicator shows short-term “syllabic-rate” expansion and gain reduction<br />
around a long-term (several seconds) average gain set. In the translator configuration,<br />
the Wideband indicator also shows relative RF signal strength.<br />
Program material and the setting of the Processing control determine the magnitude<br />
of the short-term expansion and compression (the rapid left and right movement of<br />
the green light).<br />
High-frequency program content affects the activity of the Highband indicator. With<br />
75–µsec pre-emphasis, Highband processing begins at about 2 kHz and increases as<br />
the audio frequency increases. Some programs, especially speech, may show no<br />
activity while some music programs may show a great deal of activity.<br />
3.3.3 Modulation Display<br />
A 10–segment, vertical peak-and-hold, bar graph displays the peak modulation percentage.<br />
A reading of “100” coincides with 75 kHz deviation. The display holds<br />
briefly (about 0.1 seconds) after the peak. The “Pilot” indicator illuminates when the<br />
transmitter is in the stereo mode.<br />
To verify the actual (or more precise) modulation percentage, connect a certified<br />
modulation monitor to the RF monitor jack on the rear panel.<br />
Operation<br />
3–5