Lectrosonics T2 User Manual

T2

MULTI-FREQUENCY IFB

BELT-PACK TRANSMITTER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

www.lectrosonics.com

TABLE OF CONTENTS

INTRODUCTION ................................................................................................... 3

GENERAL TECHNICAL DESCRIPTION ............................................................. 4

CONTROLS AND FUNCTIONS ........................................................................... 6

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

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

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

ADJUSTING THE TRANSMITTER FREQUENCY .............................................. 9

MICROPHONE CORD TERMINATION .............................................................. 10

5-PIN INPUT JACK WIRING ............................................................................... 11

A6U UHF ANTENNA ........................................................................................... 13

TROUBLESHOOTING ......................................................................................... 14

SPECIFICATIONS AND FEATURES .................................................................. 15

SERVICE AND REPAIR ...................................................................................... 16

RETURNING UNITS FOR REPAIR .................................................................... 16

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

The IFB T2 transmitter is FCC type accepted under Part 74: 470-608MHz and 614-802MHz

2

INTRODUCTION

Multi-Frequency IFB Belt-Pack Transmitter

Thank you for selecting the Lectrosonics IFB T2 multi-frequency, IFB transmitter. The
IFB T2 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 IFB T2 transmitter 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 IFB T2. There are 256 user selectable
frequencies in 100kHz steps to alleviate interference problems in travelling venues.
Also, the low frequency roll-off is user adjustable to adapt to varying acoustic envi­ronments and preferences.

The IFB T2 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 bronze cable that connects to a 50 Ohm SMA port on
the transmitter.

Only the IFB T2 transmitter is covered in this manual. Companion IFB receivers are
covered in separate manuals.

Rio Rancho, NM – USA

3

GENERAL TECHNICAL DESCRIPTION

The IFB T2 transmitters are comprised of a number of functional sub-systems as shown in the block diagram below.

GENERAL

The system uses 20kHz wide deviation for high signal to noise ratio. The transmitter circuits are all regulated to allow
full output power from the beginning (9 Volts) to the end (6.5 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.

COMPANDOR NOISE REDUCTION

The single band compandor is a high quality audio device that processes the input signal such that the large dynamic
ranges of input signal can be transmitted to the receiver without overload or noise. A complementary system in the
receiver recovers the original dynamics of the signal for full audio quality. Compression and expansion ratios are
complementary at 2:1. High frequency pre-emphasis is implemented in the transmitter to provide another 10dB signal
to noise improvement. Matching de-emphasis is provided in all receivers.

+5V BIAS

MIC

JACK

1
2
3
4
5

PHASE LOCKED LOOP

FREQ

SWITCHES

SUPPLY

BUFFER

SHUNT

LIMITER

DIVIDER

LF
ROLL-OFF

INPUT
AMP

LIMIT

LED

SET
LED

AUDIO
LEVEL

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

PRESCALER

LOW PASS

FILTER

LP

FILTER

COMPANDOR

Vref

+9VDC

COMPANDED

AUDIO

IFB T2 Block Diagram

PILOT
TONE

OSC

Vreg

+5VDC

Vreg

+3.6VDC

VOLTAGE

CONTROLLED

OSCILLATOR

COMPANDED AUDIO

TRANSMITTER

TO XMTR

PWR

+9VDC

PWR

LED

4

Multi-Frequency IFB Belt-Pack Transmitter

PILOT TONE SQUELCH

The IFB system utilizes an ultrasonic tone modulation of the carrier to operate the receiver squelch. This “pilot tone”
consists of a 30kHz 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.

LONG BATTERY LIFE

High efficiency circuits throughout the design allow over 4.5 hours of operation using a single 9 Volt alkaline battery.
(A 9V lithium battery will provide over 14 hours of operation.) The battery compartment is a unique mechanical
design which automatically adjusts to fit any brand of battery. The battery contacts are spring loaded to prevent
“rattle” as the unit is handled.

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 panel of the unit, provide 256 frequencies in 100kHz steps over a 25.5MHz
range. This alleviates carrier interference problems in mobile or travelling applications.

ANTENNA

At UHF frequencies, where wavelengths and antennas are shorter than at VHF frequencies, a resonant length wire is
preferred over using the microphone cable as the antenna. The antenna on the IFB T2 consists of a flexible 1/4
wavelength bronze cable, detachable via an SMA connector. The impedance of this connector is 50 Ohms.

Rio Rancho, NM – USA

5

CONTROLS AND FUNCTIONS

LECTROSONICS

IFB TRANSMITTER

ANTENNA

OFF ON

AUDIO
LEVEL

T2

0

–20

FREQUENCY

ADJUST

LF ROLL-OFF

ADJUST

75 Hz

FREQUENCY

1.6M

100K

0

0

F

F

1

E
D
C
B

A

1

E

2

2

3

3

D
C

4

4

B

5

5

6

6

A

9

9

7

7

8

8

35 150

LF ROLL OFF

INPUT JACK

The input on the IFB T2 accommodates virtually every lavalier, hand-held or shotgun microphone available. Line level
signals can also be accommodated. 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. Even when the switch is turned off or on abruptly, the pilot tone muting system
prevents “thumps” or transients from occurring.

“ON” LAMP

Glows brightly when the battery is good and the ON/OFF switch is ON. A weak or dim lamp means that the battery is
weak. When the light goes out there is about 15 to 30 minutes 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 alkaline battery. As the battery voltage drops during use, the LED brightness will
also decrease. After about 4.5 hours of operation the battery voltage will be about 6.5 Volts and the LED will be
completely out.

FREQUENCY ADJUST

These two rotary switches adjust the center frequency of the carrier. The 1.6M is
a coarse adjustment and the 100K is the fine adjustment. Each transmitter is
factory aligned at the center of its operating range. The default position of the
frequency select switches is in the center of the transmitter’s range.

0

1

F

E

D

C

B

A

2

3

4

5

6

9

7

8

0

1

F

E

D

C

B

A

2

3

4

5

6

9

7

8

6