Lectrosonics UT400 User Manual

UT400

DIGITAL-HYBRID

FREQUENCY-AGILE

HAND-HELD TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

www.lectrosonics.com

UT400

TABLE OF CONTENTS

INTRODUCTION ..................................................................................................... 3

GENERAL TECHNICAL DESCRIPTION ................................................................. 4

CONTROLS AND FUNCTIONS .............................................................................. 6

VARIMIC CONTROLS ............................................................................................. 7

BATTERY INSTALLATION ....................................................................................... 9

OPERATING INSTRUCTIONS ...............................................................................10

OPERATING NOTES .............................................................................................11

ADJUSTING THE TRANSMITTER FREQUENCY ................................................. 11

TROUBLESHOOTING ............................................................................................ 12

SPECIFICATIONS .................................................................................................13

SERVICE AND REPAIR ......................................................................................... 14

RETURNING UNITS FOR REPAIR ........................................................................14

WARRANTY ............................................................................................ Back cover

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LECTROSONICS, INC.

Digital-hybrid, Frequency Agile Handheld Transmitter

INTRODUCTION

Thank you for selecting the Lectrosonics UT400 hand-held wireless transmitter. The
UT combines over 80 years of engineering experience with the very latest components
in a design that addresses the most demanding professional applications.

The design of the UT400 was the direct result of numerous conversations with users,
staging and touring companies and dealers across the US. The specific concerns and
needs brought up in these conversations led directly to the development of the opera­tional features offered on the UT400. Two hundred fifty six frequencies are user
selectable in 100kHz steps to alleviate interference problems in travelling venues

The UT400 is an integral microphone/transmitter with an internal antenna. The antenna
is a dipole type utilizing the two printed circuit boards as the elements. The housing is
composed of durable PVC, machined to a natural, comfortable shape. Internal me­chanical parts are machined aluminum and brass.

Only the UT400 transmitters are covered in this manual. Companion receivers are
covered in separate manuals. The UT400 will operate with any 100 Series, 200 Series
and 400 Series Lectrosonics receiver in the same frequency group.

Rio Rancho, NM - USA

3

UT400

GENERAL TECHNICAL DESCRIPTION

GENERAL

The 400 system uses 75kHz wide deviation for an extremely high signal to noise ratio. The switching power supplies
provide constant voltages to the transmitter circuits from the beginning (9.3 Volts) to the end (5.5 Volts) of battery life.
The input amplifier uses an ultra low noise op amp for quiet operation. It is gain controlled with a wide range dual
envelope input compressor which cleanly limits input signal peaks over 30dB above full modulation.

DIGITAL HYBRID 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.

The Lectrosonics Digital Hybrid system 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 but a technique which
can be accomplished only in the digital domain, even though the inputs and outputs are analog signals. (As of this
writing, the patent is still pending, so we cannot reveal detailed information about the algorithm at this time.)

Channel noise still has an impact on received signal quality and will eventually overwhelm the receiver. The Digital
Hybrid 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. As always, these advantages come at a cost. The Digital Hybrid system requires fairly intensive digital
processing in both the transmitter and the receiver. These processors cost money, take up space and consume power.
The Digital Hybrid system also requires that the underlying RF link be of excellent quality, with better frequency re­sponse and distortion characteristics than that required by conventional systems.

Because it uses an analog FM link, the Digital Hybrid enjoys all the benefits of conventional FM wireless systems,
such as excellent range, efficient use of RF spectrum, and long battery life. However, unlike conventional FM sys­tems, the Digital Hybrid has done away with the analog compandor and its artifacts.

Mic

Element

Preamp

Level

Bicolor

Modulation

LEDs

Preamp

Tone

Shunt

Limiter

Input
Amp

Freq

Switches

Audio
Level

Audio

Microprocessor

A-D

Converter

11001001

Digital Signal Processor

D-A

Converter

11001001

Encoded

Audio +

Pilot Tone

9V

Battery

Switching

Power

Supply

+3.3v
+1.8v
+9v

-3v

Bicolor
Power
LED

Phase Locked Loop

Isolator

11.3 MHz

Reference

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LECTROSONICS, INC.

Voltage

Controlled

Oscillator

Final

Amplifier

50

Digital-hybrid, Frequency Agile Handheld Transmitter

NO PRE-EMPHASIS/DE-EMPHASIS

The signal to noise ratio of the 400 system is high enough to preclude the need for conventional pre-emphasis (HF
boost) in the transmitter and de-emphasis (HF roll off) in the receiver. Pre-emphasis and de-emphasis in an FM radio
system usually provides about a 10dB improvement in the signal to noise ratio of the system, but the high frequency
boost in the transmitter must be removed in a purely complementary manner or else the frequency response of the
original audio signal will be altered.

Pre-emphasis can also cause distortion in the receiver. As this signal is passed through the IF filters in the receiver,
distortion can be produced, most noticeably at full modulation. De-emphasis cannot be applied until the signal is
converted into audio, so there is no way around this problem short of eliminating pre-emphasis altogether. Neither of
these problems occur in the 400 system

PILOT TONE SQUELCH

The 400 system utilizes one of 256 different ultrasonic tones between 25 and 32 kHz, that modulate the carrier to
operate the receiver squelch. The pilot tone frequency is chosen according to which of the 256 channels has been
selected by the frequency switch setting. The basic benefit of the pilot tone squelch system is that the receiver will
remain muted until it receives the pilot tone from the matching transmitter, even if a strong RF signal is present on the
carrier frequency of the system. The UM400 extends this concept even further by insuring that all transmitters in a
system have different pilot tone frequencies so that even spurious RF from the wrong transmitters can’t open the
receiver squelch.

WIDE-BAND DEVIATION

±75kHz deviation improves the capture ratio, signal to noise ratio and AM rejection of a wireless system dramatically,
compared to the more commonly used ±15kHz deviation.

LONG BATTERY LIFE

Switching power supplies throughout the design allow over 5 hours of operation using a single 9 Volt alkaline battery. (A
9V lithium battery will provide over 14 hours of operation.) The battery contacts are spring loaded to prevent “rattle” as
the unit is handled.

FREQUENCY AGILITY

The transmitter section uses a synthesized, frequency selectable main oscillator. The frequency is extremely stable
over a wide temperature range and over time.

Two rotary switches, located under the battery door, provide 256 frequencies in 100kHz steps over a 25.5MHz range.
This alleviates carrier interference problems in mobile or traveling applications.

ANTENNA

The high output antenna utilizes the lower half of the printed circuit boards as one radiating element, with the upper half
of the PC boards and the mic capsule as the other half of the dipole configuration. This allows the mic to be held in any
position, since the user’s hands have little or no effect on the radiated power.

MICROPHONE ELEMENT

The UT400 includes the Lectrosonics VariMic mic element. The VariMic is an cardioid condenser back electret micro­phone that is adapted for the unique circumstances of wireless microphones. The problems it solves are dynamic
range, handling noise and low frequency noise (rumble or wind).

In the VariMic, an unusual pumped source FET circuit increases the usable dynamic range 12dB and greatly reduces
distortion, just as if the FET were being supplied with 48 Volts. In addition, a unique 16 position sensitivity control at the
element itself can adjust the sensitivity in 15 steps over a 15 dB range. This is in addition to the normal gain control in
the wireless microphone. The result is the widest dynamic range of any condenser mic in a wireless microphone.

The VariMic has a three point damped rubber suspension to reduce high frequency handling noise and a generous sized
windscreen to keep wind noise and breath pops away from the microphone.

Rio Rancho, NM - USA

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