Lectrosonics T195 User Manual

UT195

HAND-HELD TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

INTRODUCTION

Thank you for selecting the Lectrosonics T195 hand-held wireless transmitter. The
T195 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 T195 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 T195. This is certainly not the first hand-held
transmitter ever designed, but it is definitely the most thoroughly engineered unit
available.

The T195 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 T195 and UT195 transmitters are covered in this manual. Companion
receivers are covered in separate manuals. The T195 will operate with any 195
Series Lectrosonics receiver on the same frequency.

TABLE OF CONTENTS

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

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

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

BATTERY INSTALLATION ................................................................................... 7

OPERATING INSTRUCTIONS ............................................................................ 8

OPERATING NOTES ........................................................................................... 8

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

SPECIFICATIONS .............................................................................................. 10

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

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

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

The T195 wireless microphone is FCC type accepted under the following parts:

Part 74 (174-216 MHz) and Part 74 (470-608 MHz)

T195 / UT195 Emission Designator: 180KF3E

2

Hand-held Transmitter

GENERAL TECHNICAL DESCRIPTION

The T195 / UT195 transmitter is comprised of a number of functional sub-systems as shown in the
block diagram below.

The T195 and UT195 utilize 75kHz deviation for compatibility with the 195 series receivers. 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 33079 op amp for ultra low
noise operation and is gain controlled with a wide range input compressor which cleanly limits signal peaks up to
30dB above maximum modulation.

Compandors have long been a source of audible distortion in wireless microphone systems. The basic problem is
that when the full bandwidth of the audio signal is processed by a single compandor, the attack and decay times will
always be a compromise. If the time constants are fast, high frequency distortion will be low, however, faster time
constants in the compandor create distortion of lower frequencies. 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 distortion at an extremely low level. The low frequency compandor uses slower time con­stants, reducing low frequency distortion to well below that of a conventional compandor.

The signal to noise ratio of the 195 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 IF filtering stage in the receiver. As this signal is passed through the
IF filters in the receiver, distortion can be produced, most noticeable 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 pre­emphasis altogether. Neither of these problems occur in the 195 system. The dual-band compandor in the 195
Series system essentially provides a dynamic pre-emphasis/de-emphasis function with extremely low distortion.

MIC

ELEMENT

COMPANDED

AUDIO

PREAMP

INPUT

AMP

LIMIT

LED

SET
LED

XTAL OSC

AUDIO
LEVEL

PEAK AUDIO

INDICATOR &

FILTER

LIMITER
DRIVER

X3

LP

X2

VHF TRANSMITTER

COMPANDOR

Vref

BASS

TREBLE

COMPANDED

X2

FILTER

FILTER

AUDIO

LP

HP

Rio Rancho, NM – USA

Vreg

Vreg

XTAL OSC

PILOT
TONE

OSC

+5VDC

+3.6VDC

X4

COMPANDED AUDIO
TO XMTR

MUTE

PWR

SWITCH
DISABLE

X2 X2 X2

UHF TRANSMITTER

+9VDC

PWR
LED

LED
DISABLE

3

The 195 system utilizes a separate ultrasonic tone modulation of the basic carrier to operate the receiver squelch. A

Mod Level

LEDs

AUDIO
LEVEL

Gain Control

32kHz tone is injected into the audio signal after the microphone preamp, just after the compandor. The supersonic
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 squelched (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 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.

75kHz deviation improves the capture ratio, signal to noise ratio and AM rejection of a wireless system dramatically.
75kHz deviation is frequently used in the UHF spectrum, but it is much harder to implement at VHF frequencies. The
195 system is the first to take advantage of this wider deviation now allowed by the FCC in the VHF spectrum.
Almost all other VHF wireless systems use 15kHz deviation.

High efficiency circuits throughout the design allow over 4 hours of operation using a single 9 Volt alkaline battery
and 12 hours with a lithium battery. The battery compartment is a unique mechanical design which automatically
adjusts to fit any brand alkaline battery. Battery replacement is easily accomplished by releasing the bottom ring and
removing the battery cover. No tools are needed to change the battery. The battery is spring loaded to prevent
“rattle” as the unit is handled.

The VHF RF transmitter section is composed of a crystal stabilized main oscillator followed by a frequency tripler and
two frequency doublers. The UHF transmitter section uses a crystal stabilized main oscillator followed by quad/
double/double/double multiplier 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.

CONTROLS AND FUNCTIONS

EXTERNAL

“P” SWITCH – POWER ON/OFF

A slide switch which turns battery power on and off. The LED next to the switch lights up when the “P” switch is
turned on. This LED also serves as a battery condition indicator.
and will dim as the battery condition deteriorates. The LED is at full brightness with a new battery.
voltage reaches 7 Volts, the LED will be completely dark.

“A” SWITCH – AUDIO ON/OFF

A slide switch which “mutes” the audio in the OFF position and allows the audio gain (modulation level)
of the transmitter to be adjusted without feedback from the sound system.

INTERNAL

MOD LEVEL LEDs

These LEDs indicate the audio input level and are used when adjusting the transmitter AUDIO LEVEL (gain) control.
As the audio level increases, first one LED lights. The other LED lights as the audio level reaches maximum modula­tion. The LEDs are located underneath the battery cover, next to the AUDIO LEVEL control and are easily viewed
when holding the transmitter in a normally used position.

AUDIO LEVEL

This knob (located underneath the battery door) is operated while speaking or singing into
the transmitter to adjust the audio gain of the transmitter for the correct amount of modu­lation. The LEDs located next to it indicate the modulation level as the gain is adjusted.
See page 6 for details on this very important adjustment.

The LED will glow brightly when the battery is good

When the battery

Audio Power

On/Off On/Off

PA

4