Lectrosonics UR190 User Manual

UR190

UHF COMPACT RECEIVER

OPERATING INSTRUCTIONS

and trouble-shooting guide

LECTROSONICS, INC.

Rio Rancho, NM

INTRODUCTION

Thank you for selecting the Lectrosonics Professional Series wireless microphone system. This system
represents well over 10 years of manufacturing experience in wireless microphones, and almost 70
years of design experience.

The UR190 UHF receiver design is the result of surveying the needs of professional video producers,
ENG cameramen and many others in the broadcast and pro video industry. Hundreds of conversations
with dealers and end-users developed the final parameters for the design.

The UR190 receiver is a fixed frequency design that eliminates the need to "tune" or adjust the receiver
every time it is used. This is the preferred design for a number of reasons, among them simplicity of
operation, no adjustments in "high pressure" situations, and interference rejection by design rather than
by trying to "tune" it out.

The UR190 miniature receiver was designed by professionals for outstanding performance and
flexibility, while preserving ease of operation. It is compatible with all Lectrosonics high band
transmitters. The UR190 receiver represents one of the best values in wireless, regardless of price.

TABLE OF CONTENTS

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

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

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

RECEIVER FRONT PANEL ............................ 4

RECEIVER REAR PANEL ............................. 6

ANTENNA USE AND PLACEMENT ............................. 7

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

INDICATOR QUICK REFERENCE .............................. 8

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

UR190 REPLACEMENT PARTS AND ACCESSORIES ............... 9

SERVICE AND REPAIR ..................................... 10

RETURNING UNITS FOR REPAIR ............................. 10

SPECIFICATIONS AND FEATURES ............................ 11

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

1

GENERAL TECHNICAL DESCRIPTION

AFC

2nd Mixer

Demodulator

RF
LED

Squelch

0dB
LED

-20
LED

On

Off

Power
LED

+9V

Helical Resonator

Filter

GAsFET

Preamp

Helical Resonator

Filter

Double

Balanced

Mixer

1st

Local

Oscillator

CH12

Jack

+9V
Reg

1st IF Amp

and Crystal Filters

2nd

Local

Oscillator

Balanced

XLR

Output

Output Amp

& Level Control

2nd IF Amp
w/LC Filters

Dual-Band

Compandor

16 kHz

Lo-Pass Filter

Audio
Level

Hdph A mp

and Level Control

Headphone

Output

Polarity

Protection

Ant

Figure 1 - UR190 Receiver Block Diagram

The UR190 receiver is comprised of six major functional subsystems: the RF front-end amplifier, the
double balanced mixer/local oscillator, the first IF filter, the second IF filter and audio demodulator, the
compandor, and the balanced microphone level output circuit.

The RF front-end amplifier consists of a 5-section helical resonator for high selectivity. Between the
first and second helical resonators, is a low noise GAsFET amplifier. These amplifiers are designed to
provide only enough gain to make up for the inherent loss through the helical resonators. This
combination of low front-end gain, coupled with the extremely high selectivity of the cascaded helical
resonators results in no overloading, even on extremely strong signals. Rejection of out of band signals
is maximized, and intermodulation products are suppressed.

The mixer stage consists of a high level double balanced diode mixer. The oscillator is biased from a
regulated supply, and includes Automatic Frequency Control (AFC) yielding stable performance over
the normal variations in supply voltage. The local oscillator crystal operates at approximately 16 MHz,
and can be adjusted above and below the nominal frequency in order to place the 21.4 MHz IF in the
center of the crystal filter’s narrow passband. The high selectivity of the IF crystal filter stage further
minimizes the possibility of interference from signals on adjacent frequencies.

The second IF filter and the audio demodulator, as well as the squelch and RF output LED drive are
provided by one monolithic integrated circuit. The second IF filter is centered on 1mHz, and drives a
double tuned quadrature type FM demodulator. The squelch circuit is a supersonic noise detector type
and is factory set for a -20dB SINAD level (about .5uV). The squelch level is regulated and
temperature compensated to maintain a consistent squelch level under all conditions.

2

The Dual Band Compandor is driven by a multiple pole active low-pass filter. The filter ensures that
supersonic noise will not cause the compandor to increase gain incorrectly. This filter also drives the

-20dB and 0dB modulation LEDs.

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 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.

The compandor senses the signal level, and dynamically increases the gain for loud signals or
decreases the gain for soft signals. In this way, the original dynamic range of the transmitted signal is
restored, while preserving a high signal-to-noise ratio. The expansion ratio is 2:1, which produces a
2dB change in output signal level for a 1dB change in input level.

The balanced microphone level output circuit generates a truly balanced signal at the XLR output
connector. The volume control is a balanced attenuator, and gives a gain range from -20dBV (at full
modulation) in the fully clockwise position to -50dBV in the fully counter-clockwise position. In addition,
the headphone circuit is driven from the microphone circuit. This means that the headphone output
level is dependent not only on the headphone volume control, but also the microphone level control.

3