Solidyne 542 APC, Руководство пользователя

Страница: 24 / 44

1 – FM stereo separation degradation as a function of antena system VSWR ,
by Peter Onnigian, Jampro Antenna Company, for 31º convención AES.
3.8.3 About mono transmission
Monaural transmission, although not a very common
practice, is used by some FM stations located in cities
with a lot of congestion (and few controls and regula-
tion) in the electromagnetic spectrum. When the broad-
cast content has predominance of the spoken word
(magazzines, journalistic, news, sports) the transmission
in stereo does not bring significant advantages, since it
is only relevant for the transmission of music.
Mono FM transmission increases the coverage area of a
station, and significantly reduces interference. Transmit-
ter power, which in stereo mode is scattered over a large
bandwidth, in mono concentrates in just a quarter of the
bandwidth, increasing its effective power 4 times in the
air (See NAB Engineering Handbook). This increases the
range and eliminates the interference of nearby radios
and multipath distortion in large cities.
This technical advantage of monaural transmission can be
exploited to combat interference, improving reception and
radio coverage in times when talk shows must compete for
the audience. The station can transmit mono at certain
times and in stereo at other times.
It is even possible to switch the transmission to mono
whenever the microphones are activated, so that music and
commercial messages are always output in stereo. In this
case, if the voice of the speakers is preceded by a musical
background, it is desirable that this background music is
mono, so that when the microphones are enabled, stereo /
mono switching is inaudible (even in headphones).
The processor can switch to mono in several ways:
•
Forced by a preset. Each presets has a mono/stereo
flag. When a “mono” preset is active on-air, the
stereo coder is switched to mono. See 4.8.2 - Preset
Manager).
•
When the microphones go on-air . As in the previous
case, the switching is made by the preset change.
The GPI is used to activate the preset for “VOICES”,
which will have the “MONO” flag active. To know
how to switch the preset by GPI, see section 2.6 -
GPI).
•
Manual switching from a computer using the Lite
Commander application (requires remote IP access
to the 542APC). The operator can switch quickly to
MONO in sports or talk shows.
•
According to a schedule , using Lite Commander re-
mote software.
3.9 FM ANALYZER
542APC processor has an
FM tuner with the capability
of carry out measurements
on the received radio wave. It is available from the menu
option FM RECEIVER – ANALIZER.
3.9.1 FM Tuner
Figure 26: FM Tuner
The FM tuner has a signal analyzer monitor, that shows
several aspects on the FM transmission. It analyzes the
RF signal of the tuned station.
VERY IMPORTANT
The measurements are valid only when the radio station is
correctly tuned. If the tuned station is weak (RF Level less
than 40dB) or has strong multipatnh distortion (greater
than 10%) the measurements will not be valid. In this condi-
tion, the data fields will be hiden.
ON/OFF: Turns the tuner on/off. When the reception is poor or
isn’t possible to tune the current dial, the tuner is turned off.
FREQ: In this text field the user enters the dial in MHz, us-
ing a dot for the decimals (ie: 99.5). To tune a station pro-
ceed as follow:
•
Enter the frequency in the field “FREQ”. Press EN-
TER to confirm.
•
By pressing ENTER the station is tuned. If the
tuner was off, it turns on.
Reception Quality: Indicates if the reception of the tuned
station is adequate to validate the measurements. In case
the reception is inappropriate, the variables will be indi-
cated out of range (RF low level, Multipath, Noise, Adjacent
channel interference). When reception does not allow
measurements, the data fields are dimmed.
RF LEVEL: Shows the RF level at the 542’s antenna. The
RF level should be greater than 40dB for measurements to
be valid.
Multipath: Percentage of distortion caused by propagation
by multiple reflections of the radio wave. The level must be
less than 10% for the measurements to be valid.
Band Type: Determines the type of FM band, which varies
by region.
RBDS Mode: Activates RBDS, which is a modification of
the RDS standard used only in the USA.
Page 24 Audio Processing Core - SOLIDYNE 542 APC