Lectrosonics HML, HMM Users Manual
HM
Plug-On Transmitter
With Digital Hybrid Wireless™ Technology
INSTRUCTION MANUAL
Digital Hybrid Wireless
US Patent 7,225,135
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Purchase Date:
Rio Rancho, NM, USA
www.lectrosonics.com
HM
2
LECTROSONICS, INC.
Digital Hybrid™ Plug-On Transmitter
Thank you for selecting a Lectrosonics HM Plug-On
transmitter. The unique design provides several distinct
features for professional applications:
• OutstandingRFoperatingrange
• Superbaudioquality
• Corrosion-resistanthousing
• Programmablecompatibilitymodesforusewitha
wide variety of different receivers
™
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 HM transmitter uses a standard XLR input jack
for use with most brands of handheld mics. An LCD,
membrane switches and multi-color LEDs on the control
panel make input gain adjustments and frequency and
compatibility mode selection quick and accurate, without having to view the receiver. The battery compartment accepts AA lithium or rechargeable batteries. The
HM is machined from a solid aluminum block to provide
a lightweight and rugged package. A special non-corrosive finish resists salt water exposure and perspiration
in extreme environments.
The DSP-based design works with all Digital Hybrid
recievers, and is backward compatible for use with
Lectrosonics 200 and 100 Series and IFB receivers and
some other brands of analog wireless receivers. Companion receivers are covered in separate manuals.
Table of Contents
General Technical Description .............................................. 4
Wideband Design .................................................................. 4
Digital Hybrid Wireless
No Pre-Emphasis/De-Emphasis ........................................... 4
Low Frequency Roll-Off ........................................................ 4
Input Limiter .......................................................................... 5
Signal Encoding and Pilot Tone ............................................ 5
Microprocessor, PLL and VCO Circuits................................. 5
Compatibility Modes .............................................................. 5
Control Panel ........................................................................ 5
Wide-Band Deviation ............................................................ 5
Battery Options and Operating Time .................................... 5
Frequency Blocks .................................................................. 5
Circulator/Isolator .................................................................. 5
Controls and Functions ......................................................... 6
LCD Screen .......................................................................... 6
Power LED ............................................................................ 6
Audio Input Jack .................................................................... 6
Battery Compartment............................................................ 6
Modulation LEDs ................................................................... 6
Audio Button ......................................................................... 6
Freq Button ........................................................................... 6
Up/Down Arrows ................................................................... 6
Antenna ................................................................................. 6
Setup with the LCD ................................................................. 7
Audio Screen ........................................................................ 7
Frequency Screen ................................................................. 7
Compatibility Mode Screen ................................................... 7
Turning the Power On ........................................................... 7
Turning the Power Off ........................................................... 7
Entering the Standby Mode .................................................. 7
Lock/Unlock Screen .............................................................. 7
Battery Installation ................................................................. 8
Operating Instructions ........................................................... 9
Power Up and Boot Sequence .............................................. 9
Power Down .......................................................................... 9
Standby Mode ....................................................................... 9
Selecting the Compatibility Mode .......................................... 9
Setting Transmitter Operating Frequency ............................ 10
Adjusting the Low Frequency Roll-off ................................. 10
Attaching a Microphone and Adjusting Gain ....................... 10
Locking or Unlocking the Control Panel .............................. 11
Attaching/Removing a Microphone ..................................... 11
Accessories .......................................................................... 13
Troubleshooting .................................................................... 14
Specifications and Features ................................................ 16
Service and Repair ............................................................... 17
Returning Units for Repair .................................................. 17
™
Technology ..................................... 4
Rio Rancho, NM
3
HM
General Technical Description
Wideband Design
The HM transmitter uses ±75 kHz wide deviation for an
excellent signal to noise ratio and wide dynamic range.
The DSP controlled input limiter features a wide range
dual envelope design which cleanly limits input signal
peaks over 30 dB above full modulation. Switching power
supplies to provide constant voltages to the transmitter
circuits from the beginning (3 Volts) to the end (1.7 Volts)
of battery life, and an ultra low noise input amplifier for
quiet operation.
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 (known as
“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.
Lectrosonics Digital Hybrid Wireless™ 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.
Channel noise still impacts received signal quality and
will eventually overwhelm a receiver. Digital Hybrid
Wireless™ simply encodes the signal to use a noisy
channel as efficiently and robustly as possible, yielding audio performance that rivals that of wholly digital
systems, without the power and bandwidth problems
inherent in digital transmission.
Because it uses an analog FM link, Digital Hybrid Wireless™ enjoys all the benefits of conventional FM wireless systems, such as excellent range, efficient use of
RF spectrum, and resistance to interference. However,
unlike conventional FM systems, it does away with the
analog compandor and its artifacts.
No Pre-Emphasis/De-Emphasis
The Digital Hybrid Wireless™ design results in a signal-tonoise ratio high enough to preclude the need for conventional pre-emphasis (HF boost) in the transmitter and deemphasis (HF roll off) in the receiver. This eliminates the
potential for extreme distortion on 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 or 70 Hz to control subsonic and very
low frequency audio content in the audio. The actual rolloff 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 level sound systems, can even cause damage to loudspeaker systems.
The roll-off is normally adjusted by ear while listening
as the system is operating.
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LECTROSONICS, INC.
Digital Hybrid™ Plug-On Transmitter
Input Limiter
A DSP-controlled analog audio limiter is employed before
the analog-to-digital (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 and while preserving short term dynamics.
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 receiver’s
squelch. A pilot tone squelch system provides a reliable
method of keeping a receiver output muted (squelched)
even in the presence of significant interference. When
the system is operating in the hybrid mode, a different pilot tone frequency is generated for each carrier
frequency to prevent inadvertent squelch problems and
simplify multi-channel coordination.
Microprocessor and DSP
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.
Battery Options and Operating Time
Switching power supplies convert battery voltages to
operate various circuit stages with maximum efficiency.
With the variety of alkaline, lithium and rechargeable
NiMH batteries available today in the AA format, there
are many choices to maximize operating time or minimize cost as needed for any application.
Frequency Blocks
Lectrosonics established a “block” numbering system
years ago to organize the range of frequencies available from the low 500 MHz band to the upper 700
MHz band. Each block includes 256 frequencies in 100
kHz increments. The block number is part of a simple
formula to derive the frequency. The block number is
multiplied by 25.6 to produce the lowest frequency in
the block. For example, block 27 x 25.6 = 691.200.
Circulator/Isolator
The RF output circuit includes a one way circulator/isolator
using a magnetically polarized ferrite. This device greatly
reduces the RF intermodulation produced when multiple
transmitters are used in close proximity to one another
(several feet apart). The isolator also provides additional
RF output stage protection.
Compatibility Modes
The HM transmitter was designed to operate with
Lectrosonics Digital Hybrid receivers and will yield the
best performance when doing so. However, due to the
flexibility of digital signal processing, the transmitters
can also operate in various compatibility modes for use
with Lectrosonics 200 Series, Lectrosonics 100 Series,
IFB and certain non-Lectrosonics receivers. Contact
the Lectrosonics sales department for a complete list of
compatible non-Lectrosonics 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.
Rio Rancho, NM
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HM
Controls and Functions
Input
Coupler
XLR Input
Jack
Modulation
LEDs
PWR LED
AUDIO Button
LCD
UP Arrow
FREQ Button
LCD Screen
The LCD is a numeric-type Liquid Crystal Display with
several screens that allow settings to be made with the
AUDIO, FREQ, UP and DOWN to configure the transmitter. Turn on and turn off countdowns appear in the
LCD allowing the transmitter to be turned on for adjustments without the output stage enabled, and to prevent
accidental turn off.
Power LED
The PWR LED glows green when the batteries are
good. The color changes to red when there is about 30
minutes of operation left with the recommended lithium
batteries. Alkaline batteries will have about 20 minutes
of life left. When the LED begins to blink red, there are
only a few minutes of life.
Note: NiMH batteries will give little or no warning
when depleted. If you wish to use NiMH batteries
in the HM, we recommend trying fully charged
batteries in the unit, noting the length of time that
the batteries will run the unit and then using the
battery timer feature available on most Digital
Hybrid receivers.
A weak battery will sometimes cause the PWR LED to
glow green immediately after being put in the unit, but
will soon discharge to the point where the LED will go
red or shut off completely.
Audio Input Jack
The XLR input jack on the HM Series transmitters accommodates most hand-held microphones.
Battery Compartment
The Battery Compartment Cover Plate slides open,
allowing access to the battery compartment.
Modulation LEDs
The Modulation LEDs provide a visual indication of the
Battery
Compartment
Cover
DOWN Arrow
input audio signal level from the microphone. These two
bicolor LEDs can glow either red or green to indicate
modulation levels. 0 dB in the table below indicates full
modulation.
Signal Level -20 LED -10 LED
Less than -20 dB Off Off
-20 dB to -10 dB
-10 dB to +0 dB Green Green
+0 dB to +10 dB Red Green
Greater than +10 db
Green Off
Red Red
Audio Button
The AUDIO button is used to display the audio level setting, low frequency roll-off and phantom power mode.
Repeated pressings cycle through the settings and the
UP and DOWN arrows adjust the values.
The AUDIO 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.
The FREQ 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
operating frequency, adjust the audio level, or set the
Compatibility Mode.
Pressing both arrows simultaneously enters the lock
countdown. Holding the two arrow buttons until the
countdown completes locks the control panel buttons so
they can only be used to display current settings. “Loc”
is displayed to indicate the controls are locked.
Once locked, the buttons can be unlocked only by removing the battery, or via the RM remote control (if this
function was enabled in the transmitter setup).
Antenna
An antenna is formed between the housing and the attached microphone, operating much like a dipole type.
At UHF frequencies the length of the housing is similar
to 1/4 wavelength of the operating frequency, so the
antenna is surprisingly efficient, which helps extend the
operating range and suppress noise and interference.
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LECTROSONICS, INC.
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