Lectrosonics WM23A User Manual
WM
Watertight Transmitter
With Digital Hybrid Wireless® Technology
US Patent 7,225,135
INSTRUCTION MANUAL
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Rio Rancho, NM, USA
www.lectrosonics.com
WM
Introduction
The WM transmitter is designed to resist damage
when used in wet or dusty conditions and also offer
a comprehensive feature set that makes it equally at
home in film and television production and on stage.
A solid machined aluminum housing with a corrosion
resistant finish hosts dual battery compartments, a
moisture sealed control panel with backlit LCD and
enlarged membrane switches. Recessed seats for the
O-rings in the battery caps and input jack allow the
caps and mic connector to be tightened securely without excessive deformation of the O-rings.
The antenna is made of an extremely durable, multistrand alloy that will withstand heavy abuse. It is
mounted with a compression sealed strain relief that
prevents dust and moisture from entering the housing.
As the first stage in the signal processing chain, the
input preamp section includes very high quality, low
noise components with a wide range of gain adjustment in 1 dB increments and a DSP-controlled input
limiter. Dual color LEDs on the control panel accurately
indicate audio input level for precise gain adjustment.
Easily accessed screens on the LCD simplify setup
and adjustments.
Output power is adjustable to provide either extended
operating range or extended battery life as needed for
the application.
The Digital Hybrid Wireless® design (US Patent
7,225,135) combines 24-bit digital audio with analog
FM resulting in a system that has the same operating
range as analog systems, the same spectral efficiency
as analog systems, the same long battery life as analog systems, plus the excellent audio fidelity typical of
pure digital systems.
The DSP-based design works with all Digital Hybrid
receivers, and is backward compatible for use with
Lectrosonics 200 Series, 100 Series, IFB receivers
and some other brands of analog wireless receivers.
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LECTROSONICS, INC.
Watertight Transmitter
Table of Contents
Introduction .............................................................................................................................................................................................2
General Technical Description ..............................................................................................................................................................4
Servo Bias Input....................................................................................................................................................................................4
No Pre-Emphasis/De-Emphasis ...........................................................................................................................................................4
Low Frequency Roll-Off ........................................................................................................................................................................4
Input Limiter ..........................................................................................................................................................................................4
Signal Encoding and Pilot Tone ............................................................................................................................................................5
Microprocessor Control .........................................................................................................................................................................5
Compatibility Modes ..............................................................................................................................................................................5
Control Panel ........................................................................................................................................................................................5
Wide-Band Deviation ............................................................................................................................................................................5
Variable Power Output ..........................................................................................................................................................................5
Battery Operation .................................................................................................................................................................................. 5
Output Isolator ......................................................................................................................................................................................5
Controls and Functions .........................................................................................................................................................................6
LCD Screen ..........................................................................................................................................................................................6
Power LED ............................................................................................................................................................................................ 6
Audio Input Jack ....................................................................................................................................................................................6
Battery Compartment and Thumb Screw ..............................................................................................................................................6
Modulation LEDs ...................................................................................................................................................................................6
AUDIO Button .......................................................................................................................................................................................6
FREQ Button .........................................................................................................................................................................................6
Up/Down Arrows ...................................................................................................................................................................................6
Antenna .................................................................................................................................................................................................6
Battery Compartments ........................................................................................................................................................................... 7
About Batteries .......................................................................................................................................................................................7
Input Connector ......................................................................................................................................................................................7
Equivalent Input Circuit Diagram ..........................................................................................................................................................7
Operating Instructions ...........................................................................................................................................................................8
Power Up and Boot Sequence .............................................................................................................................................................. 8
Power Down ..........................................................................................................................................................................................8
Standby Mode .......................................................................................................................................................................................8
Menus and Settings ................................................................................................................................................................................9
UP Arrow Settings ..................................................................................................................................................................................9
Compatibility Mode ...............................................................................................................................................................................9
Input Type ..............................................................................................................................................................................................9
RF Power Output ..................................................................................................................................................................................9
LCD Backlight .......................................................................................................................................................................................9
Frequency Step Size ...........................................................................................................................................................................10
DOWN Arrow Settings .......................................................................................................................................................................... 10
Remote Control ...................................................................................................................................................................................10
Auto Power Restore ............................................................................................................................................................................10
Audio Mute ..........................................................................................................................................................................................11
FREQ Button Settings ..........................................................................................................................................................................12
AUDIO Button Settings ........................................................................................................................................................................12
Low Frequency Roll-off .......................................................................................................................................................................12
Input Gain ...........................................................................................................................................................................................12
LectroRM ...............................................................................................................................................................................................13
Troubleshooting ....................................................................................................................................................................................14
Accessories and Replacement Parts ..................................................................................................................................................16
Straight Whip Antennas .......................................................................................................................................................................17
Preventing Corrosion ...........................................................................................................................................................................18
Desiccant Battery Caps .......................................................................................................................................................................18
Battery Door Update.............................................................................................................................................................................18
Re-conditioning (drying out) the caps and desiccant beads ............................................................................................................... 19
Replacing the desiccant beads ...........................................................................................................................................................19
Specifications ......................................................................................................................................................................................20
Service and Repair ...............................................................................................................................................................................22
Returning Units for Repair ..................................................................................................................................................................22
Rio Rancho, NM
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WM
General Technical Description
Servo Bias Input
The voltage and current requirements of the wide variety of electret microphones used in professional applications has caused confusion and compromises in the
wiring needed for wireless transmitters. To address this
problem, the unique Servo Bias input circuit provides
an automatically regulated voltage over a very wide
range of current for compatibility with all microphones.
Digital Hybrid Wireless® Technology
All wireless links suffer from channel noise to some
degree, and all wireless microphone systems seek to
minimize the impact of that noise on the desired signal. Conventional analog systems use compandors for
enhanced dynamic range, at the cost of subtle artifacts
(typically “pumping” and “breathing”). Wholly digital systems defeat the noise by sending the audio information
in digital form, at the cost of some combination of power,
bandwidth and resistance to interference.
Digital Hybrid systems overcome 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 but a technique that can be accomplished only in the digital domain, even though the inputs and outputs are analog.
Because it uses an analog FM link, the Digital Hybrid
system enjoys all the benefits of conventional FM wireless systems and it does away with the analog compandor and its artifacts.
No Pre-Emphasis/De-Emphasis
The Digital Hybrid design results in a signal-to-noise ratio
high enough to preclude the need for conventional preemphasis (HF boost) in the transmitter and de-emphasis
(HF roll off) in the receiver. This eliminates the potential
for distortion of signals with abundant high-frequency
information.
Low Frequency Roll-Off
The low frequency roll-off can be set for a 3 dB down
point at 35, 50, 70, 100, 120 and 150 Hz to control
subsonic and very low frequency audio content in
the audio. The actual roll-off frequency will vary slightly
depending upon the low frequency response of the
microphone.
Excessive low frequency content can drive the transmitter into limiting, or in the case of high output sound
systems, it can even cause damage to loudspeaker
systems. The roll-off is normally adjusted by ear while
listening as the system is operating.
Input Limiter
A DSP-controlled analog audio limiter is employed before the A-D 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. It can be thought
of as two limiters in series, a fast attack and release
limiter followed by a slow attack and release limiter.
The limiter recovers quickly from brief transients, with
no audible side effects, and also recovers slowly from
sustained high levels to keep audio distortion low while
preserving short term dynamics.
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LECTROSONICS, INC.
Watertight Transmitter
Signal Encoding and Pilot Tone
In addition to controlling the limiter, the DSP also encodes the digitized audio from the A/D converter and
adds an ultrasonic pilot tone to control the squelch in
the receiver. A pilot tone squelch system provides a reliable method of keeping a receiver output muted (audio
mute) even in the presence of significant interference.
When the system is operating in the Nu Hybrid mode,
a different pilot tone frequency is generated for each
carrier frequency to prevent inadvertent squelch problems in multi-channel sytems.
Microprocessor Control
A microprocessor monitors user command inputs from
the control panel buttons and numerous other internal
signals. It works intimately with the DSP to ensure the
audio is encoded according to the selected Compatibility Mode and that the correct pilot tone is added to the
encoded signal.
Compatibility Modes
Along with providing peerless audio quality with wide
frequency response and dynamic range in Nu Hybrid
mode, the technology used in the WM Transmitter
includes compatibility modes for Lectrosonics Mode 3
and IFB receivers.
Control Panel
The control panel includes four membrane switches and
an LCD screen to adjust the operational settings. Multicolor LEDs are used to indicate audio signal levels for
accurate gain adjustment and for battery status.
Wide-Band Deviation
±75 kHz deviation improves the signal to noise ratio and
audio dynamic range of a wireless system dramatically,
compared to other designs that use ±30 kHz to 40 kHz
deviation. Wide deviation combined with a high powered transmitters makes a significant improvement in
signal to noise ratio and operating range.
Battery Operation
Switching power supplies convert battery voltages to
operate various circuit stages with maximum efficiency.
The firmware “remembers” the settings when the batteries are exhausted. After new batteries are installed,
a quick press of the AUDIO and FREQ buttons will turn
the power back on and return to the previous settings.
This is a unique behavior that takes place only when
the batteries fail during operation. If the unit is turned
off manually, a quick press of the buttons will turn it on
in the “standby” mode instead.
Because the battery caps make contact with the battery before the cap is seated, the power does not turn
back on automatically. This allows both batteries to
be installed and the caps tightened before power is
restored.
Output Isolator
The RF output circuit includes a magnetically polarized
ferrite called an isolator that suppresses IM (intermodulation) that can take place in the final amplifier.
IM in this case would result from external RF signals
from outside sources entering a transmitter through its
antenna and appearing in the final amplifier. These signals can then mix with the transmitter’s output signal to
create new interfering signals.
The isolator works like a one-way “check valve” that
lets the intended signal generated in the transmitter
travel to the antenna to be transmitted, but it directs
RF signals coming back into the antenna from outside
sources to ground and keeps them from entering the
final amplifier. This greatly reduces IM produced when
multiple transmitters are used in close proximity to one
another (several feet apart). The isolator also provides
additional RF output stage protection against static
shock.
Variable Power Output
This advanced feature allows the operator to optimize
the transmitter for maximum battery life, or for maximum operating range. Power output is selected using
the LCD in a setup mode while the RF output of the
transmitter is turned off.
Rio Rancho, NM
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WM
Controls and Functions
Modulation
LEDs
LCD
Audio
Input Jack
PWR LED
AUDIO
Button
FREQ
Button
LCD Screen
The display is a highly visible, backlit LCD with screens
for making all setup and level adjustments. The transmitter can be powered up with or without the RF output
turned on. With the RF output turned off, all adjustments can be made without creating interference for
other wireless systems in the vicinity.
For normal powering up and down, a countdown appears in the LCD. The buttons must be pressed for
the duration of the countdown, which helps to prevent
accidentally turning the transmitter on or off.
Power LED
The PWR LED glows green when the battery is good.
The color changes to red when there is about 30
minutes of operation left with the recommended lithium
battery. When the LED begins to blink red, there are
only a few minutes of life.
A weak battery will sometimes cause the PWR LED
to glow green immediately after the unit is turned on,
but will soon discharge to the point where the LED will
turn red or the unit will turn off completely. When the
transmitter is in SLEEP mode, the LED blinks green
every few seconds.
Audio Input Jack
This is a threaded locking connector that accepts the
Lectrosonics watertight WP connector.
Battery Compartment and Thumb Screw
The large knurled thumbscrews are retain the batteries
and maintain solid battery contact. The lanyard keeps
the battery caps attached, but it can be removed if
desired using a 1/16 inch hex key (Allen wrench).
UP Arrow
Battery
Compartment
Caps
DOWN Arrow
Modulation LEDs
Proper input gain adjustment is critical to ensure the
best audio quality. Two red/green LEDs will glow to accurately indicate modulation levels. The input circuitry
includes a wide range DSP-controlled limiter to prevent
distortion during high peak levels.
It is important to set the gain (audio level) high enough
to achieve full modulation during louder peaks in the
audio. The DSP-controlled limiter can handle peaks
over 30 dB above full modulation, so with an optimum
setting, the LEDs will flash red during use. If the LEDs
never flash red, the gain is too low. The -20 LED turns
red at 0 dB (full modulation).
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
AUDIO Button
The AUDIO button is used to display the gain and low
frequency roll-off settings. The UP and DOWN arrows
adjust the values. This button is also used with the
FREQ button to enter standby mode and to power the
transmitter on or off.
FREQ Button
The FREQ Button displays the selected operating frequency and also toggles the LCD between displaying
the actual operating frequency in MHz and a two-digit
hexadecimal number that corresponds to the equivalent Lectrosonics Frequency Switch Setting. This button is also used with the AUDIO button to enter standby
mode and to power the transmitter on or off.
Up/Down Arrows
The Up and Down arrow buttons are used to select the
values on the various setup screens and to lock out
the control panel. Pressing both arrows simultaneously
enters the lock countdown. When an attempt is made
to change a setting while the control panel is locked,
a message will flash on the LCD as a reminder that
the unit is locked. Once locked, the buttons can only
be unlocked by removing the batteries, or with the RM
remote control.
Antenna
The fixed whip antenna is constructed with a flexible,
woven, galvanized steel mesh cable.
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LECTROSONICS, INC.
Watertight Transmitter
d
+5 VDC
Battery Compartments
The battery compartments are a rugged, straightforward design with a recessed entry that captures
the O-ring on the cap. The spring contact on the cap
maintains solid contact on the battery regardless of its
exact length.
The O-rings should be kept clean and dry, and coated
with petroleum jelly on a regular basis. See page 11 for
more information on preventing corrosion.
Battery polarity
is marked on the
rear cover
Input Connector
The threaded WP watertight plug on the microphone cable fits into a recessed jack on the top panel. The recess
in the opening retains the O-ring when the plug is tightened. The Lectrosonics M152WP lavaliere microphone is
supplied with the WP plug already installed. Other microphones can also be terminated with this plug by following
the instructions included with the WP connector kits.
Treat O-ring with petroleum jelly before
connecting (see page 11)
Equivalent Input Circuit
Diagram
Do not cover
vent holes
•
•
•
•
•
DO NOT COVER
VENT HOLES
Unscrew battery
caps to insert
batteries
About Batteries
The transmitter is powered by two AA batteries.
Lithium batteries are recommended for longest life,
which typically provides over 7.5 hours of operation at
room temperature with the output set to 250 mW. At 50
mW, the runtime is typically over 14 hours with lithium
batteries.
The PWR LED glows green when the battery is good.
The color changes to red at a mid-point of operating
life, and will continue to glow red until the battery gets
close to the end of its life. When the LED begins to
blink red, there are only a few minutes remaining.
The exact point at which the LED turns red will vary
with battery brand and condition, temperature and current drain. The LED is simply a reminder intended to
catch your attention, not an exact indicator of remaining time.
WM Equivalent
Input Circuit Wiring
closed for mic level
open for line level
MIC
GND
(menu item)
20k
332 Ohm
200 Ohm
Servo Bias
0, 2, 4V
Roll-off
35, 50, 70, 100, 120, 150 Hz
(menu selectable)
30uF/10V
100 Ohm
+
To Limiter Control
To Virtual Groun
Audio Amplifier
Rio Rancho, NM
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WM
Operating Instructions
Power Up and Boot Sequence
Simultaneously press and hold the AUDIO and FREQ
buttons until the startup count is completed. The
screen will display a count from 1 to 3 as the unit boots
up, then it switches to the Audio screen. As the unit
turns on, the Modulation LEDs and PWR LED all glow
red, then green, and then revert to normal operation.
The LCD displays a boot sequence which consists of
four screens ending with the audio screen similar to
this example:
• Company name: Lectro
• Frequency block/Firmware Ver.: b22r2.4
• Power level: Pr 100
• Compatibility mode: CP IFB
• Audio (Input gain): Aud 22
Power Down
Simultaneously press and
hold the AUDIO and FREQ
buttons while observing that
the word “OFF” appears in the LCD along with a counter.
The screen will display a countdown from 3 to 1 and the
unit will then turn off.
Lock/Unlock the Keypad
The control panel buttons can be locked out to avoid
inadvertent changes in the settings or turning the
unit off unintentionally. Simultaneously pressing and
holding both the UP and DOWN arrow buttons during
normal operation starts a countdown timer.
The timer starts at three and counts down to zero.
When the timer reaches zero, the transmitter’s controls
are locked.
With the controls locked, the AUDIO and FREQ buttons can still be used to display current settings. Any
attempt to change a setting by pressing either the Up
or Down arrow button will result in an on-screen Loc
reminder that the controls are locked.
Once the transmitter is locked, it cannot be unlocked
or powered off using the buttons. The only ways to
unlock a locked transmitter are to remove the battery
or unlock it via the RM remote control.
Note: If the AUDIO and FREQ buttons are
released before the LCD goes blank at the end of
the countdown, the unit will not turn off. Instead,
it will stay energized and the display will return to
the previous screen.
Standby Mode
With the unit off, quickly
press both AUDIO and
FREQ buttons, and release
before counter reaches “0” to enter the “standby”
mode. In this mode the RF output is turned off so
adjustments can be made without interfering with other
systems operating in the same location. The LCD
displays rf OFF to remind you that the unit is not
transmitting.
Use the AUDIO and FREQ buttons to access the various setup screens. When the adjustments are complete, press both the AUDIO and FREQ buttons briefly
to save the settings and turn the unit off.
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LECTROSONICS, INC.
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