Lectrosonics UM450 User Manual download pdf (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

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

Retaining Screw

Location

Low Frequency

Roll-Off Control

*Not available on earlier units.

Rio Rancho, NM

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Lectrosonics UM450 User Manual Page 7

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