Medium and short wave broadcasting system; audio processor; OrbanAM9400; setting; selection
1 Preface
With the continuous progress of science and technology, all kinds of new types of radio equipment also showed a large number of emerging trends, in particular, a large number of all kinds of solid state transmitter, digital equipment and digital technology. From the current point of view, the radio emission stations and radio program production center's main task has already been changed to improve radio broadcast quality, and is no longer past that extend radio coverage and network. One of the effective ways to improve the quality of the broadcast program is to use the audio processor. The audio processor can not only handle and compress the audio signal, but also can automatically adjust the level of the broadcast program. A lot of practice has proved that in HF broadcasting system using audio processor, both to avoid appear transmitter of overmodulation, and improve the air quality, but also improve the sound effects and radio to listen to the loudness. Based on shortwave radio system audio processor OrbanAM9400 settings and options are discussed.
2 classification of audio processors
Audio processor, in short, is a device capable of processing audio signals. The audio signal is the acoustic signal which the human ear can hear, usually the frequency is between 20Hz-20kHz. Audio quality usually uses these three kinds of subjective parameters of timbre, pitch and loudness to measure. The original audio signal is the sound signal. First of all, the sound signal into electrical signal and then the nonlinear distortion, signal-to-noise ratio, frequency response and amplitude parameters to evaluate and describe the electricity in the form of audio signals. If the power form of the electrical signal of these parameters is low, then the quality of the audio signal is poor; if the parameter is high, then the quality of the audio signal is good. Based on the processing parameters of electrical signals, it can be divided into two categories: frequency processing and level processing. Based on the use of technology, it can be divided into two categories: digital audio processor and analog audio processor. The audio processing methods usually have phase processing, spectrum processing, energy processing, level processing. Phase processing is mainly the phase shifter (with a particular phase characteristics) to deal with asymmetric waveform signal and improve the waveform symmetry; frequency processing is mainly through active filter and a LC network to compensate for processing audio signals in the transmission, making,
3 audio processor OrbanAM9400 fast installation settings
Audio processor OrbanAM9400 installation is relatively simple, its rapid installation can be divided into eleven steps.
(1) audio processor OrbanAM9400 panel at the press of a button, pop-up menu is displayed, and then the system setup (system settings) selected after confirmation, enter the menu system.
(2) select the "Setup System" menu in the "Setup Quick"".
(3) the press of the handle of the audio processor OrbanAM9400 panel, enable the into "time & date" menu to set the date and time of the audio processor OrbanAM9400.
(4) the audio processor OrbanAM9400 panel handle is pressed, into a "regional setting screen menu to set the pre emphasis, pre emphasis is usually 50 microsecond or 75 g s, our budget increase of 50 microseconds.
(5) set external AGC mode.
Without AGC system exists in the audio processor OrbanAM9400 before the link, then external AGC mode should be set to no, in this way, users can OrbanAM9400 inside of the AGC mobilized using; if internal AGC to no, then external AGC mode should set to yes, in this way, users can out AGC shielding OrbanAM9400 internal.
(6) set the input level.
Into audio processor OrbanAM9400 panel "reference levels screen" (relative level settings screen menu, can be based on OrbanAM9400 of input signal types to choose whether to use a digital input, analog or (analog input), generally speaking, in order to obtain a higher quality of the input signal, the digital input, digital reference level parameters were appropriately adjusted, so that AGC attenuated header is greatly reduced.
(7) output setting (output Configure).
In the choice of whether to use a digital input or analog (analog input at the same time, should also determine whether to output preemphasis, especially for the output will be under the digital compression link caused by damage, be sure to pay attention to, must be to set the output is arranged in a flat. At the same time, the transmitter can not be set at the same time, the stereo encoder pre emphasis and processor pre emphasis, the two can only take one.
(8) set the output level.
First, in order to ensure that the transmitter modulation system to achieve 100%, it should adjust the output parameters of the audio processor OrbanAM9400.
Second, in order to ensure the loudness of program material in shortwave broadcasting system, should timely adjust the output parameters of audio processor OrbanAM9400 makes the peak clipping frequent system work.
(9) the built-in voice mode should be selected based on the channel characteristics, the audio processor OrbanAM9400 sound mode up to 46.
(10) complete the quick setup.
4 working process and technical characteristics of the audio processor OrbanAM9400
4.1 audio processor OrbanAM9400 workflow
OrbanAM9400 audio processor mainly through the composite signal level control, stereo encoder, Chong compensation, stereo enhancement unit, input filter, intelligent cut (compensation distortion and distortion control) waveform, high-frequency amplification, VCA intelligent pressure expansion unit, 5 / 2 multi band compression, two band speed automatic gain control unit etc. in a variety of ways to process the input signal, and the sound of the radio signal with some feedback network to optimize.
4.2 OrbanAM9400 audio processor technology features
For more than 20 years, ORBAN has been leading the AM broadcasting market, OrbanAM9400 is ORBAN all experience accumulated results, is 9100 and 9200 based on a leap, is the real choice of the majority of customers.
(1) OPTIMOD-AM 9400 is suitable for long wave, medium wave and short wave radio frequency system class.
(2) the gain of OPTIMOD-AM can reach 25dB, which can automatically compress the dynamic range, and make up the gain error in operation.
(3) by multi band limiting and clipping, OPTIMOD-AM can guarantee the sharpness and loudness of consistency without any audible noise, ensure the satisfaction of the audience.
(4) the built-in real-time clock, can let you in the 9400 preset time automatic operation procedures all perfectness.
(5) OPTIMOD-AM with a lineup of audio generator, you can quickly and accurately set the level of any system. This audio generator can output sine wave, square wave and triangle wave.
(6) 8 programmable, optically isolated "universal interface" (GPI) ports provided by the 5-12V pulse can be remotely controlled by OPTIMOD-AM9400.
(7) OrbanAM9400 changes everything by providing 2 separate adjustable processing chains: one is for the analog channel, one for the digital channel. Two channel processing only shared AGC and stereo stiffener, before all other processing is separate: equalizer, paragraph 5 of the pressure limiting device, a peak limiter, each of which is best matched with the corresponding channel, which reflects the 9400 unique design, and its price is much lower in box 2 configuration.
5 audio processor OrbanAM9400 selection principle
(1) after adjusting the mode of sound, be sure to pay close attention to the change of the output level. Due to the compression ratio of the signal, the audio processor OrbanAM9400 in different voice mode will also appear different signal average, the difference can even reach 8dB. In the process of converting voice mode, program listening usually changed loudness. In order to achieve better listening loudness and readjusted to the audio processor OrbanAM9400 voice patterns, be sure to the output level size were examined in detail.
(2) in the choice of the mode of audio processor OrbanAM9400, be sure to give consideration to each column of the channel, not only to maintain a certain compatibility, but also to meet the needs of most of the program. Otherwise, in the short wave radio program effect will be affected greatly in the channel program material change.
(3) the input level of the audio processor OrbanAM9400 is strictly controlled. First, to strictly calibrate the input level of the audio processor OrbanAM9400, be sure to make it in the range of -23 ~ -3dBFS (PPM). In order to avoid in shortwave radio signal due to excessive compression program distortion caused by the situation, it should be on the limiter and AGC pressure limit the proportion, the limited voltage threshold to make reasonable adjustments. A large number of practical experience shows that in order to ensure the stability of the program source signal, the peak level should be controlled in the following [6] -4dBFS.
6 Conclusion
In short, audio processor OrbanAM9400 in medium and short wave radio system application effect is better, but in setting and selection process, be sure to repeatedly test, show the distortion degree, sharpness and loudness between to find the best point of balance, in order to ensure that the medium and short wave broadcasting is the best.
