Lectrosonics UM195B Manuel utilisateur

UM195B

UHF BELT-PACK TRANSMITTER

LECTROSONICS, INC.

Rio Rancho, NM

OPERATING INSTRUCTIONS

and trouble-shooting guide

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 applica-

tions.

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

UHF Belt-Pack Transmitter

Rio Rancho, NM – USA

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 automati-

cally 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

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

PWR

XTAL OSC

X4 X2 X2 X2

UHF TRANSMITTER

Vref

BASS

TREBLE

LP FILTER

HP FILTER

SET

LED

LIMIT

LED

COMPANDOR

Vreg

+5VDC

+3.6VDC

SHUNT

LIMITER

INPUT

AMP

AUDIO

LEVEL

FILTER

PEAK AUDIO

INDICATOR &

LIMITER

DRIVER

PILOT

TONE

OSC

MIC

JACK

+5V BIAS

SUPPLY LF

ROLL-OFF

COMPANDED AUDIO

TO XMTR

COMPANDED

AUDIO

BUFFER

DELAY

+9VDC

PWR

LED

UM195B Block Diagram

CONTROLS AND FUNCTIONS

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.

ROLL-OFF

Adjustment

ANTENNA

OFF ON

–20

LECTROSONICS

UM195B

LEVEL

AUDIO

LF ROLL OFF

SN:

XXXX

35 150

75 Hz

FCC ID: DBZUM195

Lectrosonics, Inc.

Made in U.S.A.

UHF Belt-Pack Transmitter

Rio Rancho, NM – USA

MODULATION LEDS

Indicate the proper setting of the MIC LEVEL control.

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

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 pro-

duced 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!

BATTERY INSTALLATION

The transmitter is powered by a 9 Volt alkaline or lithium battery. It is important that you use ONLY an ALKALINE or

LITHIUM battery for longest life. Standard zinc-carbon batteries marked “heavy-duty”or “long-lasting”are not ad-

equate. Ni-cad rechargeable batteries will only provide 2 hours of operation, or less, and will run down quite abruptly.

The battery status circuitry is designed for the voltage drop over the life of alkaline batteries.

To open the battery compartment, press outward on the cover door in the direction of the arrow as shown in the

drawing. Only firm, sliding pressure is needed to open and close the battery door. Swing the door open and take

note of the polarity marked inside showing the location of the positive (+) and negative (-) terminals. You can see the

large and small contact holes inside the battery compartment with the door open.

Swing the

door open

Press outward on the

battery door in this

direction

Insert the battery correctly and close the cover by pressing the door closed and across, reversing the opening proce-

dure illustrated above. If the battery is inserted incorrectly, the door will not close. Do not force the door closed.

UHF Belt-Pack Transmitter

Rio Rancho, NM – USA

OPERATING INSTRUCTIONS

1) Install a fresh battery according to the instructions on the previous page.

2) Insert the microphone plug into the input jack, aligning the pins; be sure that the connector locks in.

3) Attach the antenna to the jack on the control panel of the unit. Be sure it is screwed in securely.

3) Turn the power switch to the “ON.”

4) Position the microphone in the location you will use in actual operation.

5) While speaking or singing at the same voice level that will be actually used, observe the AUDIO LEVEL LEDs.

Adjust the AUDIO LEVEL control knob until the LEDs begin to light. Start at a low setting where neither LED

lights as you speak. Gradually, turn the gain up until one LED lights, then the other.

The “-20”LED lights when the audio level is about 20dB below full modulation. The “0dB”LED lights when the

limiter begins to operate. There is over 30dB of limiting range without overload above the “0dB”LED, so it is

normal and desireable that the “0dB”LED light up 5% to 10% of the time during use.

6) Once the gain has been adjusted, the transmitter audio can be turned on to make sound system level

adjustments.

OPERATING NOTES

The AUDIO LEVEL control knob should not be used to control the volume of your sound system or recorder levels.

This gain adjustment matches the transmitter gain with the user’s voice level and microphone positioning.

If the mic level is too high —both LEDs will light frequently or stay lit. This condition may reduce the dynamic range

of the audio signal.

If the mic level is too low —neither LED will light, or the “-20”LED will light dimly. This condition may cause hiss and

noise in the audio.

The first LED turns on 20dB below full deviation. The limiting LED turns on at full deviation and indicates that the

input shunt compressor is operating. The input limiter will handle peaks over 30dB above full modulation, regardless

of the gain control setting. The limiter uses a true absolute value circuit to detect both positive and negative peaks.

The attack time is 5 milliseconds and the release time is 200 milliseconds. Occasional limiting is desirable, indicating

that the gain is correctly set and the transmitter is fully modulated for optimum signal to noise ratio.

Different voices will usually require different settings of the AUDIO LEVEL control, so check this adjustment as each

new person uses the system. If several different people will be using the transmitter and there is not time to make the

adjustment for each individual, adjust it for the loudest voice.

MICROPHONE CORD TERMINATION

VIEW FROM SOLDER

SIDE OF PINS

0.3"

0.15" Heatshrink

Tubing

TA5F Connector Assembly

Mic Cord Stripping Instructions

Caution!

Do not allow the shield wire to touch any

metal part of the connector shell.

The shield wire is the antenna on VHF

models and poor operating range will result.

Shield Wire

Crimp

Tabs

Rubber

Insulation

Crimp

Tabs

Rubber

Insulation

Note: This termination is required on VHF transmitters and will still work fine on UHF transmitters.

UHF Belt-Pack Transmitter

Rio Rancho, NM –USA

Transmitter

Input Jack

LECTROSONICS

1uH

10K

100

330PF

5V Mic Bias

5mA max

To Mic Amp

POS BIAS (OR GND)

MIC

SOURCE LOAD

LINE IN

NEG GND (OR BIAS)

UHF Transmitter Equivalent Input Circuit

5-PIN INPUT JACK WIRING

The wiring diagrams shown on the separate sheet represent the basic wiring necessary for the most common types

of microphones and other audio inputs. Some microphones may require extra jumpers or a slight variation on the

diagrams shown.

Caution - When wiring the connector, do not use the connector body for any electrical connections.

A common mistake is to use the connector body as an audio ground. The connector body is

already used as an RF ground on VHF models and no other use is permitted.

It’s virtually impossible to keep completely up to date on changes that other manufacturers make to their products. It

is possible that you may encounter a microphone that differs from these instructions. If this occurs please call our toll-

free number listed on page 13 of this instruction manual. Our service department can answer your questions regard-

ing microphone compatibility.

When used on a wireless transmitter, the microphone element is in the proximity of the RF coming from the transmit-

ter. The nature of electret microphones makes them sensitive to RF, which can cause problems with the microphone/

transmitter compatibility. If the electret microphone is not designed properly for use with wireless transmitters, it may

be necessary to install a chip capacitor in the mic capsule or connector to block the RF from entering the electret

capsule. This modification is shown on the next page.

VHF transmitters use the shield of the microphone cord as the antenna. The UM195B uses a 1/4 wave flexible wire to

radiate the RF signal. There is really not much difference between these two approaches, with respect to the effect of

the RF on the microphone capsule. Even in transmitters that utilize a “dangling wire,”the microphone is still part of

the “ground plane”and is therefore still in the antenna circuit.

PIN 1 Shield (ground) for positive biased electret lavalier microphones. Bias voltage source for negative biased

electret lavalier microphones. Shield (ground) for dynamic microphones and line level inputs.

PIN 2 Shield (ground) for negative biased electret lavalier microphones. Bias voltage source for positive biased

electret lavalier microphones.

PIN 3 Low impedance microphone level input for dynamic microphones. Also accepts hand-held electret micro-

phones provided the microphone has its own built-in battery.

PIN 4 1K Ohm source load for non-Lectrosonics electret microphones. Use in conjunction with other pins to provide

attenuation of high level input signals.

PIN 5 High impedance, line level input for tape decks, mixer outputs, musical instruments, etc.

RF BYPASSING

Some mics require RF protection to keep the radio signal

from affecting the capsule, even though the transmitter

input circuitry is already RF bypassed (see schematic

diagram).

If the mic is wired as directed, and you are having

difficulty with squealing, high noise, or poor frequency

response; RF is likely to be the cause.

The best RF protection is accomplished by installing RF

bypass capacitors at the mic capsule. If this is not

possible, or if you are still having problems, capacitors

can be installed on the mic wires inside the TA5F connector housing.

Install the capacitors as follows: Use 330 pF capacitors. Capacitors are available from Lectrosonics. Please specify

the part number for the desired lead style.

Leaded capacitors: P/N 15117 Leadless capacitors: P/N SCC330P

All Lectrosonics lavalier mics are already bypassed and do not need any additional capacitors installed for proper

operation.

BODY GROUND

Caution - When wiring the connector, do not use the connector body for any electrical connections. A common

mistake is to use the connector body as an audio ground. The connector body is already used as an RF ground on

VHF models and no other use is permitted.

LINE LEVEL SIGNALS

The normal hookup for line level signals is: Signal Hot to pin 5, Signal Gnd to pin 1, pin 4 jumped to pin 1, and pin 3

jumped to pin 1. This gives a 40dB attenuator that allows signal levels much higher than 3V to be applied without

distortion.

If more headroom is needed, insert a 100k resistor in series with pin 5. Put this resistor inside the TA5F connector to

minimize noise pickup.

If lower than normal line levels (less than 1V) are expected, use this hookup: Signal Hot to pin 5, Signal Gnd to pin 1,

and pin 4 jumpered to pin 1. This provides a 20dB attenuator allowing signals as high as 3V to be applied without

distortion.

WIRING HOOKUPS FOR DIFFERENT SOURCES

3 WIRE MIC2 WIRE MIC

CAPSULE CAPSULE

SHIELD

AUDIO

SHIELD

AUDIO

BIAS

TA5F

CONNECTOR

TA5F

CONNECTO

Preferred locations for bypass capacitors

Alternate locations for bypass capacitors

SHIELD

AUDIO

BIAS

3 WIRE ELECTRET MIC

POSITIVE BIAS

TA5F

PLUG

SHIELD

AUDIO

2 WIRE ELECTRET MIC

POSITIVE BIAS

TA5F

PLUG

SHIELD

BIAS

AUDIO

WIRE ELECTRET MIC

NEGATIVE BIAS

TA5F

PLUG

SHIELD

AUDIO

2 WIRE ELECTRET MIC

NEGATIVE BIAS

TA5F

PLUG

SHIELD

TIP

SLEEVE

LINE LEVEL

RCA or 1/4 " PLUG

AUDIO 1

TA5F

PLUG

DYNAMIC

MIC LEVEL

PIN PIN

SHIELD

Dynamic LO Z mic or electret with

manufacturers power supply.

TA5F

PLUG

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