Lectrosonics WM/VT500WATER Data Sheet

WM

Digital Hybrid Wireless®
Watertight Belt-Pack Transmitter

WM, WM/E01, WM/E02, WM/X

• Selectable output power (50, 100, 250 mW) to
maximize battery life or operating range

• Machined aluminum, corrosion resistant housing

• Water resistant seals for use in wet environments

• LCD interface with lockout option

• Programmable compatibility modes for use with a
wide variety of different receivers (varies with model;
see Specifications)

• Servo Bias input circuitry with selectable voltage

To meet the demand for both extended operating range
and extended battery life, the transmitter offers select­able output power of 50, 100 and 250 mW. With higher
power output, the operating range is improved at the
expense of battery life. When range is not an issue, the
power can be reduced to extend the battery life.

The transmitter can be controlled by the LectroRM
app for hands free setup and adjustment using audible
tones delivered into the microphone from your phone.
The transmitter can be put to sleep to conserve battery
power during setup when it is buried deep inside cos­tuming, then awakened for normal operation when the
production begins. Other adjustments include frequency,
audio level and control panel lockout.

Designed for wet or dusty environments, the WM trans­mitter features O-ring sealed battery compartments and
input jack, a compression sealed antenna port, and gas­ket sealed control panel and back cover. Dual AA batter­ies provide twice the operating time of earlier watertight
transmitter designs. Larger membrane switches and
control panel and a highly visible, backlit LCD enhance
the user interface.

Digital Hybrid Wireless® is a revolutionary new design

that combines digital audio with an analog FM radio link to
provide outstanding audio quality and the exemplary RF
performance of the finest analog wireless systems.

This overcomes channel noise in a dramatically new way,
digitally encoding the audio in the transmitter and decoding
it in the receiver, yet still sending the encoded information
via an analog FM wireless link. This proprietary algorithm
is not a digital implementation of an analog compandor.
Instead, it is a technique which can be accomplished only
in the digital domain.

The process eliminates compandor artifacts, expanding the
applications to include test and measurement of acoustic
spaces and musical instruments.

*US Patent 7,225,135

The DSP-based design works with all Digital Hybrid re­ceivers, and is backward compatible for use with Lectro­sonics Mode 3 and IFB.

The input section features servo bias circuitry with
voltages being selectable from the LCD to match the
requirements of a wide variety of lavaliere microphones.
The bias can also be turned off for use with dynamic
microphones. A line level setting is provided for use with
signal levels up to 5 volts. The low frequency roll-off can
be adjusted from 35 to 150 Hz.

A DSP-controlled analog audio limiter is employed ahead
of the first mic preamp to protect the entire audio chain
from overload. The limiter has a range of more than 30
dB for excellent overload protection and a dual release
envelope that makes the limiter acoustically transparent
while maintaining low distortion.

TECHNICAL DATA

Rio Rancho, NM, USA
www.lectrosonics.com

Watertight Connections

The input connector is mounted in a recessed open­ing which provides a captive seat for the O-ring on the
microphone connector. This captures the O-ring allowing
it to be tightened firmly.

The antenna is mounted with a compressible strain
relief under a flange that presses the strain relief into a
tapered opening for a watertight connection.

Input Limiter

A DSP-controlled analog audio limiter is employed
before the analog-to-digital converter. The limiter has a
range of more than 30 dB for excellent overload protec­tion. A dual release envelope makes the limiter acousti­cally transparent while maintaining low distortion. The
limiter recovers quickly from brief transients, so that its
action is hidden from the listener, but recovers slowly

WM Transmitter Block Diagram

from sustained high levels, to keep audio distortion low
and preserve short term dynamic changes.

The bicolor LEDs on the control panel accurately indi­cate limiter activity to assist in setting the input gain for
optimal signal to noise ratio and dynamic range.

DSP-Based Pilot Tone & Compatibility

The DSP generated pilot tone eliminates the need for
fragile crystals and allows a different pilot tone frequency
for each of the carrier frequencies in the tuning range of
the wireless system. Individual pilot tones significantly
reduce squelch problems in multichannel systems where
a pilot tone signal can appear in the wrong receiver via
intermodulation products.

The DSP also offers compatibility modes to allow back­ward compatibility with all Lectrosonics Mode 3 and IFB
systems, in addition to its Nu Hybrid operating mode.

Output Isolator

The transmitter RF output circuit includes a specialized
RF device called an isolator using a magnetically polar­ized ferrite to allow RF signals to pass through to the
antenna, but block them from coming backward into the
transmitter output section.

The isolator greatly reduces RF intermodulation produced
in the transmitter output stages when multiple units are
used in close proximity (a few feet apart). The isolator also
helps protect the output stage from electrostatic shock
delivered to the antenna. Isolators are common in broad­cast and commercial applications, but because of their
high cost it is unusual to find them in wireless microphone
transmitters.