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CR187
Compact Receiver
INSTRUCTION MANUAL
Fill in for your records:
Serial Number:
Purchase Date:
Rio Rancho, NM, USA
www.lectrosonics.com
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CR187
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LECTROSONICS, INC.
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Compact Receiver
Table of Contents
Introduction.............................................................................................................................................................................................4
General Technical Description ..............................................................................................................................................................4
CR187 Block Diagram...........................................................................................................................................................................4
Controls and Functions .........................................................................................................................................................................5
Receiver Front Panel.............................................................................................................................................................................. 5
Modulation LEDs...................................................................................................................................................................................5
Output Control.......................................................................................................................................................................................5
EXT/OFF/INT Switch ............................................................................................................................................................................5
Power LED ............................................................................................................................................................................................5
RF LED .................................................................................................................................................................................................5
Receiver Rear Panel ...............................................................................................................................................................................6
12 VDC Input.........................................................................................................................................................................................6
Audio Output XLR Jack.........................................................................................................................................................................6
Mini Phone Jack....................................................................................................................................................................................6
Antenna Terminal ..................................................................................................................................................................................6
Battery Replacement.............................................................................................................................................................................. 7
Antenna Use and Placement .................................................................................................................................................................8
Operating Instructions...........................................................................................................................................................................9
Troubleshooting......................................................................................................................................................................................9
Replacement Parts and Accessories..................................................................................................................................................10
Specifications and Features................................................................................................................................................................ 10
Service and Repair ...............................................................................................................................................................................11
Returning Units for Repair ..................................................................................................................................................................11
Introduction
The CR187 receiver design originated in the late 1980’s with a feature set intended for camera mounted ENG applications. It’s fixed frequency design included extremely sharp front-end filters and narrowband crystal filters in the IF
stage, which likely explains its continued use in today’s crowded RF environment.
The receiver operates on a single 9V battery or external DC power, allowing it to be used in a wide variety of applications in broadcast and film production, ENG and with almost any pro sound equipment.
Rio Rancho, NM
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CR187
General Technical Description
The block diagram of the receiver provides a basic
overview of the major circuit sections.
The RF front-end amplifier consists of three cascaded
pairs of helical resonators for high selectivity. Between
the three resonators are two low noise grounded gate
JFET amplifiers. These amplifiers are designed to provide only enough gain to make up for the 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, 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
pass band. The high selectivity of the crystal filter stage
further minimizes the possibility of interference from
signals on adjacent frequencies.
One monolithic integrated circuit filters the second
IF, demodulates the audio, provides squelch control
and drives the RF output LED. The second IF filter is
centered on 1 MHz and drives a double tuned quadrature type FM demodulator. The squelch circuit is a
supersonic noise detector type and is factory set for a
-20 dB SINAD level (about .5 uV). The squelch level is
regulated and temperature compensated to maintain a
consistent squelch level under all conditions.
The overall wireless system utilizes “compandor”
noise reduction, which consists of a compressor in the
transmitter and expander in the receiver. The receiver
decodes (expands) the compressed signal coming from
the transmitter in a 2:1. The process 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 and the signal-to-noise ratio is increased
significantly. De-emphasis (HF roll-off) is also applied
to reverse the pre-emphasis (HF boost) applied in the
transmitter as an additional noise reduction technique.
The expander circuit is driven by a multiple pole active
low-pass filter. The filter ensures that supersonic noise
will not cause the expander to increase gain incorrectly.
This filter also drives the -20 dB modulation LED.
The output of the receiver is a balanced microphone
level signal delivered on an XLR connector. The output
level control is actually a balanced attenuator to adjust
the signal from -20 dBV in the fully clockwise position
to -50dBV in the fully counter-clockwise position. This
preserves the signal to noise ratio regardless of what
output level is set.
A separate output is provided to drive headphones
separately from the main XLR output. The level is affected by both the main output control and a secondary
trimpot on the side panel.
Warning: The CR187 is a negative ground
device. Do not connect this receiver to a
positive ground device through the audio
cabling. Damage to either device could result.
CR187 Block Diagram
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LECTROSONICS, INC.
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Controls and Functions
-50 -20
RF
LECTROSONICS
CR187
MODULATION
-20 0dB
OUTPUT
dBV
EXT
OFF
BATT
POWER
INT
FCC ID: DBZ7F7CR185
Lectrosonics, Inc.
Made in USA
S/N: XXXX
This device complies with part
15 of the FCC rules. Operation
is subject to the condition that
this device does not cause
harmful interference.
MIN
MAX
Headphone Level
Side and Front Panels
Compact Receiver
Modulation LEDs
The Modulation LEDs indicate the audio level of the incoming signal. The -20 LED glows when the transmitter
modulation is at a high enough level to produce a good
audio signal-to-noise ratio. The 0 dB LED indicates the
transmitter modulation is at maximum. If both the -20
and 0 dB LEDs are glowing constant, this indicates the
transmitter’s gain is set too high. It is normal and desirable that you see the -20 LED glowing with an occasional flicker of the 0 dB lamp in typical use.
Mini Phone Jack
The Miniphone Jack provides a audio monitor, separate
from the rear panel XLR audio output. The output level
from this jack is controlled by both the front panel OUTPUT control and the Headphone Level trim-pot on the
side panel. Generally, the front panel OUTPUT control
would be set to provide the proper output level at the
rear panel XLR jack, then the side panel trim-pot is adjusted to match the required level for your headphones.
The output at this mini connector is designed for a
medium impedance headphone/earphone. An impedance between 30 and 300 Ohms will usually provide
adequate volume. The sound from a low impedance
headphone (i.e.. 8 Ohms) will not be very loud and may
be distorted at higher listening levels.
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 counterclockwise position of the OUTPUT control, the output level
of this XLR jack will be -50 dB at full modulation. In the
fully clockwise position, the output level will be -20 dB at
full modulation.
EXT/OFF/INT Switch
The EXT/OFF/INT switch turns the receiver power off
and on and selects either internal 9 Volt battery power,
or an external 12 VDC power source (of either polarity).
Power LED
The Power LED glows when adequate power is supplied from either the internal battery or an external
source. If this LED is very dim or does not light up when
the switch is turned on, replace the battery or check the
connections from the external power source.
The Power LED is connected to a precision battery test
circuit that continuously monitors battery voltage. It is at
full brightness with a new 9 VDC alkaline battery. As the
battery voltage drops during use, the LED brightness
will also decrease. After 4 to 5 hours, the battery voltage will be about 7 volts and the LED will be completely
extinguished. From 6.5 volts to 6 volts, the receiver will
still operate, but with degraded performance. Below
6 volts, the regulated and temperature compensated
squelch circuit will cease to be regulated.
Warning: When the battery voltage drops below
6 Volts, the power LED will remain off, but the
other three LEDs (-20 0dB and RF) will light up
and a loud rush of audio noise will be heard as
the squelch opens. This condition is normal,
and is easily remedied by replacing the battery.
RF LED
The RF LED glows when the associated transmitter is
turned on and the receiver has a good signal. When the
carrier signal from the transmitter is too weak to produce a clean audio signal, this lamp will go out as the
squelch engages and mutes the audio.
Antenna Terminal
The Antenna Terminal can be connected to any VHF
antenna with a bandwidth that covers the frequency of
the receiver and terminates with a 50 ohm BNC type
connector. A flexible whip antenna is supplied.
Headphone Level Adjustment
This recessed trim-pot on the side panel is a secondary
level control for the mini jack output on the front panel. It
does not affect the main XLR output on the rear panel.
Normally the main output level is set to match the camera, mixer or recorder, which also affects the output of
the mini jack. Then the headphone level is adjusted with
this trim-pot for a comfortable listening level.
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CR187
Receiver Rear Panel
Main Output XLR Jack 12 VDC Input
Audio Output XLR Jack
The Audio Output XLR Jack supplies a balanced, low
impedance output at microphone level. The audio signal
is output on pins 2 and 3, while pin 1 is ground. The
output level of this jack is controlled by the OUTPUT
control on the front panel of the receiver.
12 VDC Input
The 12 VDC Input connects to the supplied CH-12 AC
adapter for powering the receiver from a 110/120V
AC source. The receiver may also be powered from
other external 12 VDC sources using the correct plug
(Switchcraft S-760 power plug). Although the CR187 is
a negative ground device, a diode bridge is used in the
external power input, so that the CR187 will operate
properly from either polarity.
Warning: Because the CR187 is a negative
ground device, do not connect this receiver
to a positive ground device through the audio
cabling. Damage to either device could result.
Battery Replacement
The CR187 is powered by a standard alkaline 9 volt
battery. It is important that you use ONLY an ALKALINE
battery for longest life. Standard zinc-carbon batteries
marked “heavy duty” or “long-lasting” are not adequate.
They will provide only about one hour of operation.
Similarly, nicad rechargeable batteries give less than 2
hours of operation, and will also run down quite abruptly. Alkaline batteries provide about 5 hours of operation.
To open the battery compartment, press outward on
the cover door in the direction of the arrow as shown in
the drawing. Only slight, 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.
Insert the battery and close the cover by pressing in
and across, reversing the opening procedure outlined
above. Note that the battery door will NOT close if the
battery is inserted incorrectly, since the terminals will hit
a protective polarity barrier. Do not force the battery in.
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LECTROSONICS, INC.
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Operating Instructions
1) Connect the power cord or install the battery. (The
CR187 is a negative ground device. Do not connect
this receiver to a positive ground device through
the audio cabling. Damage to either device could
result.)
2) Attach and extend the antenna.
3) Connect the audio cable.
4) Set the front panel switch to either “EXT” or “INT”,
depending upon the power source. Check to see
that the red POWER LED lights up.
5) THIS IS CRITICAL STEP IN THE SET UP PROCEDURE TO ACHIEVE OPTIMUM SIGNAL TO
NOISE RATIO. Adjust the transmitter “gain” for full
modulation and slight limiting on signal peaks. See
your transmitter manual for specific directions on
the proper gain adjustment of your transmitter.
6) Adjust the output control according to the type of input on your equipment. The input levels on different
VCR’s and PA equipment vary, which may require
that you set the OUTPUT control in an intermediate position. Try different settings and listen to the
results. If the output of the receiver is too high, you
may hear distortion or a loss of the natural dynamics of the audio signal. If the output is too low, you
may hear steady noise (hiss) along with the audio.
The CR187 output was designed to drive microphone level inputs. The output signal level ranges
from -50dBV with the output control fully counter
clockwise to -20dBV with the output control fully
clockwise.
Compact Receiver
On the M187 transmitter, the MIC LEVEL control and
LEVEL and LIMIT LEDs are used to set the input gain
for optimum signal to noise ratio.
Rio Rancho, NM
On the H187 transmitter, the LEVEL control on the rear
panel and LEVEL and LIMIT LEDs on the top panel
next to the input connector are used to set the input
gain for optimum signal to noise ratio.
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CR187
Antenna Use and Placement
Connect the antenna to the front panel jack. Position the
antenna so that it is not touching any metallic surfaces.
It is also good to position the receiver so that there is a
direct “line of sight” between the transmitter and the receiver antenna. In situations where the operating range
is less than about 50 feet, the antenna positioning is
much less critical.
A wireless transmitter sends a radio signal out in all
directions. This signal will often bounce off nearby walls,
ceilings, etc. and a strong reflection can arrive at the receiver antenna along with the direct signal. If the direct
and reflected signals are out of phase with each other
a cancellation may occur. The result would be a “drop
out.” A drop out sounds like either audible noise (hiss),
or in severe cases, may result in a complete loss of the
carrier and the sound. Moving the transmitter even a
few inches may eliminate it. A dropout situation may be
either better or worse as a crowd fills and/or leaves a
room, or when the transmitter or receiver is operated in
a different location.
Example mounting locations
for single or multiple receiver(s).
Dropouts can be avoided by careful placement of the
receiver. If you are mounting the receiver on a video
camera or camcorder, experiment with the location prior
to going into the field. By placing the antenna above
the body of the camera, you will increase your operating range. If the antenna is laid next to the camera, as
shown in the illustration below, the body of the camera
will serve as a shield and reduce range. This position
may work but be certain at least part of the antenna
extends above the camera.
If dropouts occur in the field, moving the transmitter or
receiver slightly in any direction will usually eliminate
the problem.
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LECTROSONICS, INC.
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Compact Receiver
Troubleshooting
Before proceding, ensure that you have a good battery in the receiver (or a properly connected AC adapter) and that
the POWER LED is glowing brightly.
SYMPTOM POSSIBLE CAUSE
NO POWER LED 1) Receiver switch in “OFF” position
NO RF LED 1) Transmitter not turned on
RF LED ON BUT NO SOUND AND NO MODULATION LEDS
2) Dead or weak battery
3) External 12 Volt power disconnected
4 )CH-12 AC adapter disconnected
5) Receiver switch in wrong position for the power source used
2) Transmitter battery dead
3) No microphone on transmitter (the microphone serves as
the antenna
4) Receiver antenna not connected
1) Transmitter switch in “MUTE” position
2) Transmitter microphone not connected
3) Microphone switch in “OFF” position
4) Possible malfunction in the audio section of the transmitter.
See transmitter manual.
5) Check transmitter modulation LEDs for possible transmitter problem
MODULATION LED’s ON BUT NO SOUND 1) Receiver LEVEL control turned down.
2) Audio cable disconnected
3) Recorder or sound system off, or not properly adjusted.
Rio Rancho, NM
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CR187
Replacement Parts and Accessories
Part No. Description
CH-12 110 Volt AC adapter for CR187 receiver
A-185 Coax Remote, folded-dipole antenna with
35753 System pouch
A-195RA Helical, flexible (“rubber duckie”) antenna
A-185-BNC Telescoping 1/4 wave whip on a swiveling
coaxial cable
with a 9inch whip and a right angle BNC
connector
BNC connector
Specifications and Features
Operating Frequencies: 150MHz to 216MHz, crystal controlled
Sensitivity: Better than 0.6uV for 20dB quieting without compandor;
Signal/Noise Ratio: 102dB A weighted
Squelch Quieting: greater than 100dB
AM Rejection: -60dB (10uV to 0.1 Volts)
Modulation Acceptance: ±15kHz
Image and Spurious Rejection: greater than 100dB
Third Order Intercept: +6dBm
Audio Outputs: XLR: 200 Ohms balanced; 100mV max.
Antenna Input: BNC; 50 Ohms impedance
Controls: XLR front panel output attenuator control
Indicators: Red LED for power “ON” (Battery status)
Power Requirements: 12 Volts DC external (either polarity)
Power consumption: 55mA
Battery Life: 5 hours with alkaline
Weight: 11 ounces including battery
Dimensions: 1.1” x 2.75” x 5.2”
1.9uV for 50dB S/N ratio with compandor
Headphone: 2 Volts RMS into 100 Ohms
Recessed trim-pot headphone control
3 position power/function switch
2 LEDs for modulation level
“RF” LED for transmitter “ON”
110 VAC via CH-12 AC adapter
Single 9 Volt alkaline battery
Specifications subject to change without notice.
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LECTROSONICS, INC.
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Compact Receiver
Service and Repair
If your system malfunctions, you should attempt to correct or isolate the trouble before concluding that the equipment
needs repair. Make sure you have followed the setup procedure and operating instructions. Check the interconnecting
cables and then go through the Troubleshooting section in this manual.
We strongly recommend that you do not try to repair the equipment yourself and do not have the local repair shop attempt anything other than the simplest repair. If the repair is more complicated than a broken wire or loose connection,
send the unit to the factory for repair and service. Don’t attempt to adjust any controls inside the units. Once set at the
factory, the various controls and trimmers do not drift with age or vibration and never require readjustment. There are
no adjustments inside that will make a malfunctioning unit start working.
LECTROSONICS’ Service Department is equipped and staffed to quickly repair your equipment. In warranty repairs
are made at no charge in accordance with the terms of the warranty. Out-of-warranty repairs are charged at a modest
flat rate plus parts and shipping. Since it takes almost as much time and effort to determine what is wrong as it does
to make the repair, there is a charge for an exact quotation. We will be happy to quote approximate charges by phone
for out-of-warranty repairs.
Returning Units for Repair
For timely service, please follow the steps below:
A. DO NOT return equipment to the factory for repair without first contacting us by letter or by phone. We need to
know the nature of the problem, the model number and the serial number of the equipment. We also need a
phone number where you can be reached 8 A.M. to 4 P.M. (U.S. Mountain Standard Time).
B. After receiving your request, we will issue you a return authorization number (R.A.). This number will help speed
your repair through our receiving and repair departments. The return authorization number must be clearly shown
on the outside of the shipping container.
C. Pack the equipment carefully and ship to us, shipping costs prepaid. If necessary, we can provide you with the
proper packing materials. UPS is usually the best way to ship the units. Heavy units should be “double-boxed” for
safe transport.
D. We also strongly recommend that you insure the equipment, since we cannot be responsible for loss of or dam-
age to equipment that you ship. Of course, we insure the equipment when we ship it back to you.
Mailing address: Shipping address: Telephone:
Lectrosonics, Inc. Lectrosonics, Inc. (505) 892-4501
PO Box 15900 581 Laser Rd. (800) 821-1121 Toll-free
Rio Rancho, NM 87174 Rio Rancho, NM 87124 (505) 892-6243 Fax
USA USA
Web: E-mail:
www.lectrosonics.com sales@lectrosonics.com
Rio Rancho, NM
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LIMITED ONE YEAR WARRANTY
The equipment is warranted for one year from date of purchase against defects in
materials or workmanship provided it was purchased from an authorized dealer. This
warranty does not cover equipment which has been abused or damaged by careless
handling or shipping. This warranty does not apply to used or demonstrator equipment.
Should any defect develop, Lectrosonics, Inc. will, at our option, repair or replace any
defective parts without charge for either parts or labor. If Lectrosonics, Inc. cannot
correct the defect in your equipment, it will be replaced at no charge with a similar new
item. Lectrosonics, Inc. will pay for the cost of returning your equipment to you.
This warranty applies only to items returned to Lectrosonics, Inc. or an authorized
dealer, shipping costs prepaid, within one year from the date of purchase.
This Limited Warranty is governed by the laws of the State of New Mexico. It states the
entire liablility of Lectrosonics Inc. and the entire remedy of the purchaser for any
breach of warranty as outlined above. NEITHER LECTROSONICS, INC. NOR
ANYONE INVOLVED IN THE PRODUCTION OR DELIVERY OF THE EQUIPMENT
SHALL BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE, CONSEQUENTIAL,
OR INCIDENTAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THIS EQUIPMENT EVEN IF LECTROSONICS, INC. HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. IN NO EVENT SHALL THE LIABILITY OF
LECTROSONICS, INC. EXCEED THE PURCHASE PRICE OF ANY DEFECTIVE
EQUIPMENT.
This warranty gives you specific legal rights. You may have additional legal rights which
vary from state to state.
581 Laser Road NE • Rio Rancho, NM 87124 USA • www.lectrosonics.com
(505) 892-4501 • (800) 821-1121 • fax (505) 892-6243 • sales@lectrosonics.com
7 December 2007
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