Lectrosonics UCR190 User Manual
UCR190
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 UCR190 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 UCR190 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 UCR190 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 UCR190 receiver represents one of the
best values in wireless, regardless of price.
TABLE OF CONTENTS
INTRODUCTION .................................................................................................. 2
GENERAL TECHNICAL DESCRIPTION ............................................................ 3
CONTROLS AND FUNCTIONS .......................................................................... 4
RECEIVER FRONT PANEL ................................................................................. 4
RECEIVER REAR PANEL ................................................................................... 6
BATTERY REPLACEMENT ................................................................................. 6
ANTENNA USE AND PLACEMENT ................................................................... 7
OPERATING INSTRUCTIONS ............................................................................ 8
INDICATOR QUICK REFERENCE ...................................................................... 8
TROUBLESHOOTING ......................................................................................... 9
REPLACEMENT PARTS AND ACCESSORIES ................................................. 9
SERVICE AND REPAIR ..................................................................................... 10
RETURNING UNITS FOR REPAIR ................................................................... 10
SPECIFICATIONS AND FEATURES ................................................................ 11
WARRANTY ......................................................................................... Back cover
2
GENERAL TECHNICAL DESCRIPTION
C
UHF Compact Receiver
Ant
Helical Resonator
Filter
H12
Jack
Polarity
Protection
GAsFET
9V
Battery
+9V
Reg
Helical Resonator
Preamp
Off
Ext
Filter
1st
Local
Oscillator
Int
Batt
+9V
Power
LED
Double
Balanced
Mixer
1st IF Amp
and Crystal Filters
AFC
Balanced
XLR
Output
Headphone
2nd
Local
Oscillator
Output
2nd Mixer
Output Amp
& Level Control
Hdph Amp
and Level Control
UCR190 Receiver Block Diagram
RF
LED
2nd IF Amp
w/LC Filters
Demodulator
Dual-Band
Compandor
Audio
Level
0dB
LED
-20
LED
Squelch
Lo-Pass Filter
16 kHz
The UCR190 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 entire life of the
battery. 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.
Rio Rancho, NM – USA
3
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.
CONTROLS AND FUNCTIONS
RECEIVER FRONT PANEL
LECTROSONICS
UCR190
OFF
dBV
EXT
-
20
-
MODULATION
-
20
Headphone adjustment
on side panel.
0dB
50
OUTPUT
MODULATION LEDs
Indicate the modulation (audio level) of the incoming signal, and can be used for proper adjustment of the
transmitter’s “MIC LEVEL” or “GAIN”. The -20 LED glows when the transmitter modulation is at a high enough level to
produce a good audio signal-to-noise ratio. It will normally flicker, or stay lit as you speak into the microphone. The
0dB lamp indicates a “peak,” showing that the transmitter modulation is at maximum. Constant lighting may indicate
that the audio gain in the transmitter may be set too high. It is normal and desirable that you see an occasional flicker
of the 0dB lamp in typical use.
OUTPUT CONTROL
Attenuates the audio output level of the receiver to match the input requirements of the equipment with which it is
used. The XLR output jack on the rear panel provides an audio output at microphone level for low impedance,
balanced inputs. At the extreme counter-clockwise position of the control knob, the output level of this XLR jack will
be 50dB at full modulation. In the fully clockwise position, the output level will be -20dB at full modulation. Intermediate settings are sometimes necessary due to the variations in different input compressors and ALC (automatic level
control) circuits on various VCR’s and audio inputs. The markings around the control knob are provided simply as
“memory markers;” they are not calibrated with reference to a specific output level.
POWER
INT
BATT
RF
4
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