Lectrosonics UM190 User Manual

UM190

UHF BELT-PACK TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

INTRODUCTION

Thank you for selecting the Lectrosonics UM190 belt-pack transmitter. The UM190 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 UM190 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 UM190. This is certainly not the first belt­pack transmitter ever designed, but it is definitely the most thoroughly engineered unit available.

The UM190 is a rugged, machined aluminum package with a removable, spring loaded belt clip. The input section
provides a correct input tap for virtually any microphone or line level audio source. 5 Volts of bias voltage is
available to power electret mics with either positive or negative bias. Level indicating LEDs are provided on the
control panel to make level settings quick and accurate, without having to view the receiver. The battery
compartment accepts any 9 Volt alkaline battery and makes a positive connection via self-adjusting contacts. The
antenna is a detachable, locking 1/4 wavelength flexible wire that connects to a 50 Ohm port on the transmitter.

Only the UM190 transmitter is covered in this manual. Companion receivers are covered in separate manuals.
The UM190 will operate with any 190 Series Lectrosonics receiver on the same frequency.

TABLE OF CONTENTS

INTRODUCTION .......................................... 1

GENERAL TECHNICAL DESCRIPTION .......................... 2

CONTROLS AND FUNCTIONS ................................ 4

BATTERY INSTALLATION ................................... 6

OPERATING INSTRUCTIONS ................................. 7

OPERATING NOTES ....................................... 7

UM190 INPUT JACK WIRING ................................. 8

TROUBLESHOOTING ....................................... 9

SPECIFICATIONS AND FEATURES ............................ 10

SERVICE AND REPAIR ..................................... 11

RETURNING UNITS FOR REPAIR ............................. 11

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

The UM190 transmitter is FCC type accepted under Part 74: 470-608 MHz

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GENERAL TECHNICAL DESCRIPTION

MIC

+5V BIAS

JACK

Vref

BASS

TREBLE

LP FILTER

HP FILTER

SET
LED

LIMIT

LED

COMPANDOR

Vreg

Vreg

+5VDC

+3.6VDC

COMPANDED

AUDIO

XTAL OSC

X4

X2 X2 X2

UHF TRANSMITTE R

+9VDC

PWR
LED

SHUNT

LIMITER

-9V

ONMUTE

OFF

SUPPLY

INPUT
AMP

AUDIO
LEVEL

LP

FILTER

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

X2

The UM190 transmitter is comprised of a number of functional sub-systems as shown in the block diagram below.

The 190 system uses 15kHz deviation. 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 oscillator crystal is shock mounted to provide
ruggedness. 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.

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 190 system introduces an entirely new approach to solving this basic problem, called "dual-band companding."

There are actually two separate compandors in the 190 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.

Figure 1 - UM190 Block Diagram

High efficiency circuits throughout the design allow over 7 hours of operation using a single 9 Volt alkaline battery.
The battery compartment is a unique mechanical design which automatically adjusts to fit any brand alkaline
battery. The battery contacts are spring loaded to prevent "rattle" as the unit is handled.

The UHF transmitter section uses a crystal stabilized main oscillator followed by a quadrupler and three doubler
stages. The crystal controlled frequency is extremely stable over a wide temperature range and over time. Double
tuning used in the multiplier stages provides higher attenuation of spurious emissions which, in turn, minimizes the

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possibility that the transmitter RF output would interfere with another transmitter/receiver system operating in the
same vicinity.

At UHF frequencies, where wavelengths and antennas are shorter than VHF, a resonant dangling wire is preferred.
The antenna on the UHF version of the UM190 consists of a flexible ¼ wavelength wire, detachable via a twist lock
connector. The impedance of this connector is 50 Ohms at UHF frequencies.

CONTROLS AND FUNCTIONS

LECTROSONICS

UM190

ON

MUTE

OFF

LEVEL

LIMIT

MIC LEVEL

LF

ROLL-OFF

ADJ

30Hz

150Hz

Figure 2 - M190 Controls and Functions

INPUT JACK

The input on the UM190 accommodates virtually every lavalier, hand-held or shotgun microphone available. Use a
Switchcraft TA5F connector on the cord. See the separate sheet titled "UM190 Input Jack Configuration"

regarding the correct connections for various microphones, and other sources.

ON/MUTE/OFF SWITCH

Turns the battery power on and off. The center position is an "audio mute" which should be used when setting the
MIC LEVEL control to turn off the sound from the microphone during this adjustment. Even when the switch is
turned off or on aburptly, the pilot tone muting system prevents "thumps" or transients from occurring.

"ON" LAMP

Glows brightly when the battery is good. A weak or dim lamp means that the battery is weak, and has about half
an hour of operation left. If the lamp fails to light, the battery should be replaced. The power lamp should light up
in both the "MUTE" and "ON" positions of the POWER/MUTE SWITCH.

The "ON" lamp is connected to a precision battery test circuit that continuously monitors battery voltage. The LED
is at full brightness with a new 9 Volt alkaline battery. As the battery voltage drops during use, the LED brightness
will also decrease. After about 7 hours the battery voltage will be about 7 Volts and the LED will be completely out.

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