Lectrosonics UM195b User Manual

UM195B

UHF BELT-PACK TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

www.lectrosonics.com

UM195B

INTRODUCTION

Thank you for selecting the Lectrosonics UM195B belt-pack transmitter. The
UM195B 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 UM195B was the direct result of numerous conversations with
users 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 UM195B. This is certainly not the first belt-pack transmitter ever
designed, but it is definitely the most thoroughly engineered unit available.

The UM195B 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 is available on the input connector 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 or
lithium 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 UM195B transmitter is covered in this manual. Companion receivers are
covered in separate manuals. The UM195B will operate with any 190 Series
Lectrosonics receiver on a matching frequency.

TABLE OF CONTENTS

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

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

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

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

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

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

MICROPHONE CORD TERMINATION ................................................................ 8

5-PIN INPUT JACK WIRING ................................................................................. 9

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

SPECIFICATIONS AND FEATURES .................................................................. 12

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

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

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

The UM195B transmitter is FCC type accepted under Part 74: 470-608 MHz

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LECTROSONICS, INC.

UHF Belt-Pack Transmitter

+5V BIAS

SUPPLY

MIC

LF

JACK

1
2
3
4
5

PWR

XTAL OSC

X4

X2

X2

X2

UHF TRANSMITTER

Vref

BASS

TREBLE

LP FILTER

HP FILTER

SET
LED

LIMIT

LED

COMPANDOR

Vreg

Vreg

+5VDC

+3.6VDC

INPUT

LEVEL

AMP

AUDIO

LP

FILTER

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

PILOT
TONE

OSC

ROLL-OFF

COMPANDED AUDIO

TO XMTR

COMPANDED

AUDIO

BUFFER

DELAY

+9VDC

PWR

LED

SHUNT

LIMITER

GENERAL TECHNICAL DESCRIPTION

The UM195B transmitter is comprised of a number of functional sub-systems as shown in the block diagram below.

The 195 system uses +/-75kHz 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 195 system
introduces an entirely new approach to solving this basic problem, called “dual-band companding.”

There are actually two separate compandors in the 195 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.

High efficiency circuits throughout the design allow over 7 hours of operation using a single 9 Volt alkaline battery
(over 16 hours with a lithium 9V 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
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 UM195B consists of a flexible ¼ wavelength wire, detachable via an SMA

<--See 5-Pin Input Jack Wiring for details.

connector. The impedance of this connector is 50 Ohms at UHF frequencies.

UM195B Block Diagram

Rio Rancho, NM – USA

3

UM195B

LECTROSONICS

UM195

CONTROLS AND FUNCTIONS

B

OFF ON

AUDIO
LEVEL

ANTENNA

–20

0

ROLL-OFF
Adjustment

75 Hz

35

LF ROLL OFF

LF

FCC ID: DBZUM195

150

Lectrosonics, Inc.

Made in U.S.A.

SN:

XXXX

INPUT JACK

The 5-pin input jack accommodates virtually every lavalier, hand-held or shotgun microphone available. Use a
Switchcraft TA5F connector on the cord. See the separate sheet titled “Transmitter 5-Pin Input Jack Wiring” regarding
the correct connections for various microphones, and other sources.

ON/OFF SWITCH

Turns the battery power on and off.

“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 “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 battery. As the battery voltage drops during use, the LED brightness will also
decrease. When the LED is barely visible, there will still be 30 minutes or more operating time remaining.

Since the internal circuits are all tightly regulated and the RF output stage has a separate discrete regulator, the
transmitter will continue to operate to a battery voltage of 6.5 Volts. From 6.5 Volts to 6 Volts, the transmitter will still
operate, but with degraded performance. Please note that a weak battery will sometimes light the POWER LED
immediately after turn on, but will soon discharge to the point where the LED will go out, just like a flashlight with
“dead” batteries.

The combination of an accurate battery condition indicator and regulation of all internal circuits provides much longer
battery life, as well as consistent performance over the life of the battery.

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LECTROSONICS, INC.

MODULATION LEDS

Indicate the proper setting of the MIC LEVEL control.

LEVEL LED -- Flickers or glows when sufficient audio is present.

UHF Belt-Pack Transmitter

LIMIT LED -- Lights up when the input level is high enough to cause limiting. The input limiter has a very high

overload threshold (over 30 dB). Generally speaking, some limiting is desirable in normal operation to improve
the signal to noise ratio of the system. The limiting action is not audible and does not create distortion. A highly
trained ear would hear only the compression of the peaks in the audio signal, which is desirable with most tape
recorders and many sound reinforcement systems.

MIC LEVEL

Used to adjust the audio input level for the proper modulation.

ANTENNA JACK

The flexible wire antenna supplied with the transmitter is cut to 1/4 wavelength. It is removable via an SMA connector.
The 50 Ohm RF port can also be connected directly to test equipment.

ADJUSTABLE LOW FREQUENCY ROLL-OFF

A 18dB per octave low frequency roll-off is provided in the audio section, with the -3dB point adjustable from 35Hz to
150Hz. The actual roll-off frequency will vary somewhat according to the low frequency response of the mic capsule
being used.

The low frequency roll-off control is used to prevent undesirable subsonic (or very low frequency) audio, often pro­duced by air conditioning systems, automobile traffic and other sources from causing the compandor to mistrack.
Excessive low frequency content in the audio input can cause “pumping and breathing” of background noise or
modulation of the program audio in recording applications. In sound reinforcement systems, excessive low frequency
content can cause excessive power amplifier drain or even damage to loudspeaker systems. By rotating the control
clockwise, the hinge point of the roll-off is increased to reduce the level of low frequencies. In controlled situations,
such as a motion picture production set indoors where environmental noise is minimal, the control can be rotated
counter-clockwise to permit low frequency audio to be captured.

THE BELT CLIP

The belt clip may be removed for special applications by removing one screw.

USE ONLY THE SCREW THAT IS SUPPLIED

The circuitry is tightly packed into this unit. A longer screw will permanently damage the transmitter!

Rio Rancho, NM – USA

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