3-8
OPERATION
ORBAN MODEL 9300
steep rolloff above that frequency. The steepness of the rolloff eliminates the
possibility of improving the audio through preemphasis. In our opinion, these
radios must be written off as producing hopelessly bad sound. Very few people
would enjoy listening to music on these radios
although they could be used for
listening to talk programs, or for repelling pigeons and muggers.
The vast majority of present-day radios are in the second and third categories. In all
three types of radio, bass performance is completely unpredictable from model to
model. The best-sounding “Group 1” AM receiver we know of is the Sony SRF-A100
AM stereo radio (now discontinued), which can be switched between wideband and
narrowband operation. Use headphones, or drive an external amplifier and speaker
with the Sony's headphone output (its own tiny speakers cannot be used for reference
purposes). A representative good-sounding wideband mono radio is the General
Electric Superadio. In “Group 2,” we are fond of the Radio Shack MTA- series of small
table radios. The last time we looked, the model number was up to MTA-17, but these
numbers are updated periodically. Moreover, there is no guarantee that Radio Shack
will continue to sell this series.
Be aware that many radios produce excessive distortion all by themselves, especially if
they are located near the transmitter. If the station monitor (driven through
OPTIMOD-AM's monitor rolloff filter) sounds clean but your radio audio is distorted,
don't trust the radio! If the General Manager's auto radio sounds distorted, he or she
should not jump to the conclusion that there is something wrong with the station or
with the engineer's ears.
Modulation Monitors
Many modulation monitors and RF amplifiers indicate higher modulation than the
transmitter is actually producing. This forces the engineer to reduce transmitter
modulation unnecessarily, which can cost you up to 3dB of loudness! It is
very
important
to be sure that your modulation monitor is accurately calibrated and that it
does not exhibit overshoot on program material. Several newer monitors are designed
for accurate pulse response without overshoot. Any of these monitors will enable you
to obtain the highest loudness achievable from your transmitter and antenna system.
If the monitor is used remotely, be sure that the RF amp doesn't overshoot. Overshoots
in RF amps have been observed to be as high as 3dB.
Monitor readings should be compared with an oscilloscope observing the modulated
RF envelope. If the monitor indicates 100% negative peaks when the oscilloscope
reveals no carrier pinch-off, suspect inaccuracy in the monitor.
More About Audio Processing
Psychoacoustic factors were considered carefully during the design and construction of
OPTIMOD-AM. The resulting audio processor is easy to use (the
L
ESS
-M
ORE
control
greatly simplifies setup) and produces a sound that is remarkably free from unwanted
processing artifacts.
Although the controls on OPTIMOD-AM provide the flexibility you need to customize
your station's sound, proper adjustment of these controls consists of balancing the
trade-offs between loudness, density, brightness, and audible distortion. In
Summary of Contents for OPTIMOD-AM 9300
Page 1: ...Operating Manual OPTIMOD AM 9300 Digital Audio Processor Version 2 0 Software...
Page 7: ...Operating Manual OPTIMOD AM 9300 Digital Audio Processor Version 2 0 Software...
Page 178: ...3 46 OPERATION ORBAN MODEL 9300...
Page 200: ......
Page 221: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 21...
Page 222: ...6 22 TECHNICAL DATA ORBAN MODEL 9300 CONTROL BOARD PARTS LOCATOR...
Page 228: ...6 28 TECHNICAL DATA ORBAN MODEL 9300...
Page 229: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 29 I O DSP BOARD LEFT AND RIGHT ANALOG INPUTS...
Page 230: ...6 30 TECHNICAL DATA ORBAN MODEL 9300 I O DSP BOARD ANALOG OUTPUTS...
Page 231: ...OPTIMOD AM DIGITAL TECHNICAL DATA 6 31...
Page 238: ...6 38 TECHNICAL DATA ORBAN MODEL 9300 FRONT VIEW REAR VIEW FRONT PANEL PARTS LOCATOR DIAGRAM...