Lectrosonics UM450 - Manual (Page 7)

Frequency Synthesized UHF Belt-Pack Transmitter
Modulation LEDs
The Modulation LEDs provide a visual indication of the
input audio signal level from the microphone. These
two bicolor LEDs can glow either red or green to indi­
cate modulation levels.
Signal Level -20 LED -10 LED
Less than -20 dB Off Off
-20 dB to -10 dB Green Off
-10 dB to +0 dB Green Green
+0 dB to +10 dB Red Green
Greater than +10 dB Red Red
The Modulation LEDs are also used to indicate the
Compatibility Mode when the transmitter is initially
turned on. The Modulation LEDs will blink simultane­
ously:
• Once for 100 Series mode
• Two times for 200 Series mode
• Three times for mode 3
• Four times for Digital Hybrid Wireless ® or
400 Series mode
• Five times for IFB mode*
• Six times for mode 6
Modes 3 and 6 provide compatibility with other manu­
facturer’s receivers - contact the factory for details.
Antenna
The flexible galvanized steel cable antenna supplied
with the transmitter is cut to 1/4 wavelength of the cen­
ter of the frequency block (the frequency range) of the
transmitter. It is removable via an SMA connector. The
SMA connector is a 50 Ohm RF port which can also
be connected directly to test equipment. Replacement
antennas are available in pre-cut lengths for specific
frequency blocks, or as a kit with instructions to cut the
antenna for any frequency block.
Frequency Select Switches
Two 16-position rotary switches adjust the center fre­
quency of the carrier. The 1.6M is a coarse adjustment
and the 100K is the fine adjustment.
Adjustable Low Frequency Roll-Off
A 18dB per octave low frequency roll-off is provided in
the audio section, with the -3dB point adjustable from
35Hz to 150Hz. The actual roll-off frequency will vary
somewhat according to the low frequency response of
the mic capsule being used.
The low frequency roll-off control is used to remove
subsonic (or very low frequency) audio, often produced
by air conditioning systems, automobile traffic and other
sources. Excessive low frequency content in the audio
input can cause a variety of audio problems including
driving the transmitter into limiting. In sound reinforce­
ment systems, as one instance, excessive low frequen­
cy content can cause excessive power amplifier drain
or even damage to loudspeaker systems. By rotating
the control clockwise, the hinge point of the roll-off is
increased to reduce the level of low frequencies. In
controlled situations, such as a motion picture produc­
tion set indoors where environmental noise is minimal,
the control can be rotated counter-clockwise to permit
low frequency audio to be captured.
Belt Clip
The belt clip may be removed for special applications by
removing one screw.
WARNING: Use ONLY the screw that is
supplied.
The circuitry is tightly fitted into this unit. A longer
screw will permanently damage the transmitter!
Belt Clip Belt Clip
Retaining Screw
Location
Low Frequency
Roll-Off Control
*Not available on earlier units.
Rio Rancho, NM 7