Orban OPTIMOD-AM 9300, Руководство по эксплуатации

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OPTIMOD-AM DIGITAL INTRODUCTION
1-7
Computer Interface
On the rear panel of the 9300 are an RS-232 serial port and a 100 Mbps Ethernet
port for interfacing to IBM-compatible PCs either locally or through a TCP/IP net-
work. These computer interfaces support remote control and metering, and allow
downloading software upgrades.
Each 9300 package ships with 9300 PC Remote software, an application for any IBM-
compatible PC running Microsoft Windows 2000 (Service Pack 3 or higher) or XP.
9300 PC Remote permits you to adjust any 9300 preset by remote control or to do
virtually anything else that you can do from the 9300’s front panel controls. The
program displays all of the 9300’s LCD meters on the computer screen to aid remote
adjustment.
RS-232 Serial Port
9300 PC Remote can communicate at up to 115 kbps via modem or direct connection
between the computer and the 9300 through their RS-232 serial ports.
RJ45 Ethernet Connector
The 9300 can be connected to any Ethernet network that supports the TCP/IP proto-
col.
See Networking and Remote Control on page 2-41 for more information.
Location of OPTIMOD-AM
Optimal Control of Peak Modulation Levels
The audio processing circuitry in OPTIMOD-AM produces a waveform that is pre-
cisely peak-controlled to prevent overmodulation, and is lowpass filtered to protect
adjacent channels and to conform to government regulations. Severe changes in the
shape of the waveform can be caused by passing it through a circuit with non-
constant group delay and/or non-flat frequency response in the 30-9500Hz range.
Deviation from flatness and phase linearity will cause spurious modulation peaks be-
cause the shape of the peak-limited waveform is changed. Such peaks add nothing
to average modulation. Thus, the average modulation must be lowered to accom-
modate those peaks so that they do not overmodulate. Transformers can cause such
problems.
Landline equalizers, transformers, and low-pass filters in transmitters typically intro-
duce frequency response errors and non-constant group delay. There are three crite-
ria for preservation of peak levels through the audio system:
1) The system group delay must be essentially constant throughout the frequency
range containing significant energy (30-9,500Hz). If low-pass filters are present,
this may require the use of delay equalization. The deviation from linear-phase
must not exceed

1

from 30-9,500Hz.