Lectrosonics Venue (Narrowband) - Manual (Page 13)

Digital Hybrid Wireless™ Modular Receiver System
Three diversity reception modes are available:
• Switched Diversity uses one receiver module per
audio channel.
• Ratio Diversity (OptiBlend TM ) uses two receiver
modules per audio channel.
• Frequency Diversity uses two receiver modules
and two transmitters per audio channel.
Press the Receiver Select Buttons to enter the setup
screens for the receiver modules.
Switched Diversity
In this mode the signals from both antennas are com­
bined into a single receiver module, with the phase of
one of them inverted back and forth so that they always
add to one another. The process reduces dropouts and
provides a stronger signal than a single antenna.
Ratio Diversity (OptiBlend
TM
)
Ratio diversity uses two adjacent receiver modules to
pick up a single transmitter. The audio outputs of the
modules are blended (mixed) together, using more or
less audio from each module based upon which module
has the stronger RF signal.
Ratio diversity anticipates dropouts before they occur,
rather than waiting until the RF signal level is very weak
and on the verge of noise or dropout. The comparison
of the RF signal levels in the modules begins when the
RF level is still high, so the circuit can blend in more
audio from the module with the stronger signal before
the signal decays enough to cause noise.
The blending action is smooth and seamless to avoid
any audible artifacts that can occur with abrupt switch­
ing. Most of the time both receiver modules have good
signals, so the audio is blended equally, which improves
the signal to noise ratio by 3 dB.
The blended audio appears at the rear panel XLR out­
puts of both modules.
Frequency Diversity
Frequency Diversity differs from the other two diversity
modes in that it uses two receiver modules and two
transmitters operating on different frequencies. The pur­
pose of this mode is to have redundancy in the system
for critical productions, such as live television, to guard
against failures caused by dead batteries and multipath
dropouts. The blending process to combine the audio
from the receiver modules is the same as that used for
OptiBlend ratio diversity.
Frequency Diversity requires that the levels of the two
audio channels to be closely matched to avoid au­
dible level changes as the blending action takes place.
In order for this blending to work properly, a special
test mode helps to get the transmitter levels exactly
matched. The test mode is automatically activated when
the DivMode Setup Screen is active and Frequency
Diversity is selected, as shown in the LCD photo above.
Note: In Frequency Diversity mode, both
transmitters must be the same type (usually the
same model). The microphones must also be
placed very close together to minimize comb
filtering.
To prepare for operation in the Frequency Diversity
mode, make the following adjustments:
1 . Set up the transmitters according to their instruc­
tions. Plug a set of headphones into the front panel
PHONES jack to monitor the blended output. You
can also monitor the output from the rear panel
XLR jack for either module in the pair.
2. While listening to the blended output, adjust the
gain control on one of the transmitters so that the
audio loudness drops way down (nulls) as the two
channels cancel each other. If the output does not
null, then reset the transmitter input gain control
back to where it was and press the Function button
on the front panel next to the word INVT on the
LCD. This will invert the phase of the audio on the
second module so it will null properly.
INVT shown in Off Position
Rio Rancho, NM, USA 13