Lectrosonics UT300VM User Manual

UT300

FREQUENCY-AGILE

HAND-HELD TRANSMITTER

EURO MODEL WITH VARI-MIC CAPSULE

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

www.lectrosonics.com

0885

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Frequency Agile Handheld Transmitter, Euro Model

INTRODUCTION

Thank you for selecting the Lectrosonics UT300 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 UT300 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 UT300.

The UT300 can store up to 256 frequencies with a minumum of 25 kHz spacing, as
programmed by the dealers and service centers to meet local allocations and legal
requirements.

The UT300 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.

Only the UT300 transmitters are covered in this manual. Companion receivers are
covered in separate manuals. The UT300 will operate with any 300 Series Lec­trosonics receiver in the same frequency group.

TABLE OF CONTENTS

INTRODUCTION ................................................................................................... 2

GENERAL TECHNICAL DESCRIPTION ............................................................. 3

CONTROLS AND FUNCTIONS ........................................................................... 5

BATTERY INSTALLATION ..................................................................................... 8

OPERATING INSTRUCTIONS ............................................................................. 9

OPERATING NOTES ............................................................................................. 9

ADJUSTING THE TRANSMITTER FREQUENCY ............................................ 10

TROUBLESHOOTING......................................................................................... 11

SPECIFICATIONS ............................................................................................... 12

SERVICE AND REPAIR ...................................................................................... 13

RETURNING UNITS FOR REPAIR .................................................................... 13

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

Rio Rancho, NM - USA

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GENERAL TECHNICAL DESCRIPTION

The UT300 transmitters are comprised of a number of functional sub-systems as shown in the block diagram below.

GENERAL

The 300 system uses 50kHz wide deviation for an extremely high signal to noise ratio. The transmitter circuits are all
regulated to allow full output power from the beginning (9 Volts) to the end (7 Volts) of battery life. The input amplifier
uses a Motorola 33078 op amp for ultra low noise operation. It is gain controlled with a wide range input compressor
which cleanly limits input signal peaks over 30dB above full modulation.

DUAL BAND COMPANDOR

Traditionally, compandors have been a source of distortion in wireless microphone systems. The basic problem with
conventional systems is that the attack and decay times are always a compromise. If the time constants are fast, high
frequency transients will not be distorted, but this will cause low frequency distortion. If the time constants are slower,
low frequency audio distortion will be low, but high frequency transients will then be distorted. The 300 system
introduces an entirely new approach to solving this basic problem, called “dual-band companding.”

There are actually two separate compandors in the 300 system, one for high frequencies and one for low frequencies.
A crossover network separates the frequency bands at 1kHz with a 6dB per octave slope, followed by separate high
and low frequency compandors. The attack and release times in the high frequency compandor are fast enough to
keep high frequency transient distortion at a low level, and the low frequency compandor uses slower time constants,
reducing low frequency distortion to well below that of a conventional compandor.

NO PRE-EMPHASIS/DE-EMPHASIS

The signal to noise ratio of the 300 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 300 system. The dual-band compandor in the 300 Series system essentially provides a
dynamic pre-emphasis/de-emphasis function with extremely low distortion.

MIC

ELEMENT

PHASE LOCKED LOOP

SWITCHES

SHUNT

LIMITER

FREQ

PREAMP

DIVIDER

LIMIT

LED

SET
LED

INPUT
AMP

AUDIO
LEVEL

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

PRESCALER

LOW PASS

FILTER

LP

FILTER

Vref

BASS

TREBLE

COMPANDED

COMPANDOR

LP FILTER

HP FILTER

AUDIO

PILOT
TONE

OSC

Vreg

+5VDC

Vreg

+3.6VDC

VOLTAGE

CONTROLLED

OSCILLATOR

COMPANDED AUDIO

MUTE

TRANSMITTER

TO XMTR

PWR

+9VDC

PWR

LED

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Frequency Agile Handheld Transmitter, Euro Model

PILOT TONE SQUELCH

The 300 system utilizes an ultrasonic tone modulation of the carrier to operate the receiver squelch. This “pilot tone”
consists of a 32kHz signal mixed with the audio signal following the microphone preamp, just after the compandor, to
control the audio output muting of the receiver. The pilot tone is filtered out of the audio signal immediately after the
detector in the receiver so that it does not influence the compandor or various gain stages. 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. This is extremely important in
applications such as with an automatic microphone mixer.

WIDE-BAND DEVIATION

50kHz deviation improves the capture ratio, signal to noise ratio and AM rejection of a wireless system dramatically.
Almost all other wireless systems use less than 50kHz deviation.

LONG BATTERY LIFE

High efficiency circuits throughout the design allow over 8 hours of operation using a single 9 Volt alkaline battery (18
to 20 hours with a new lithium battery.) The battery compartment is a unique mechanical design which automatically
adjusts to fit any brand of alkaline or lithium battery. Battery replacement is easily accomplished by releasing the
bottom and removing the battery cover. The battery contacts are spring loaded to prevent “rattle” as the unit is
handled. The UT300 contains a battery status monitoring circuit which monitors and sends the battery status to the
UDR200B receiver. The battery status is displayed on the front of the receiver.

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 on the side of the unit will select from up to 256 frequencies as programmed by the
dealers or service centers to meet local allocations and avoid interference problems.

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 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 UT300 includes the Lectrosonics VariMic mic element. The VariMic is a 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.

Low frequency noise is much more of a problem with wireless microphones than with conventional microphones.
With a regular mic, low frequency wind noise, breath thumps or handling rumble can be filtered out at the control
board before the noise causes problems with the following electronics or speaker systems. But with a wireless
microphone, the electronics that will be overdriven are right in the wireless microphone. Filtering at the control board
is much too late. To solve this problem, the VariMic has a low frequency filter that is so sharp that it can remove low
frequency noise without affecting any wanted vocals. It consists of a 36 dB per octave filter circuit to sharply remove
low frequency noise below 75 Hz without affecting vocal fundamentals. The lowest operatic bass voice fundamental is
82 Hz. Isn’t it nice to know that it will come ripping right through.

Rio Rancho, NM - USA

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