Comtek Communications Technology BST75 Transmitter User Manual Drawing dwg

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Document ID	518760
Application ID	0RV9xLOyFNBOGywWiM92Ng==
Document Description	USERS MANUAL
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Permanent Confidential	No
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Document Type	User Manual
Display Format	Adobe Acrobat PDF - pdf
Filesize	74.19kB (927423 bits)
Date Submitted	2005-02-28 00:00:00
Date Available	2005-02-24 00:00:00
Creation Date	2005-02-22 12:03:35
Producing Software	Acrobat Distiller 5.0 (Windows)
Document Lastmod	2005-02-22 12:03:53
Document Title	Drawing.dwg
Document Creator	ADOBEPS4.DRV Version 4.50
Document Author:	BEER

BST-75 OPERATOR’S MANUAL
(72-76 MHz)
Synthesized
Base Station
Transmitter
357 West 2700 South • Salt Lake City, Utah 84115 • Phone: (800) 496-3463 • Fax: (801) 484-6906 • www.comtek.com
TABLE OF CONTENTS
Introduction ...........................................................
Equipment Placement ...............................................
Power Requirements .......................................................
Remote Antenna ......................................................
Screw-in Whip Antenna ............................................
Audio Input Connections ...............................................
Audio Adjustments ...............................................
Audio Processing Circuit ..........................................
Front and Rear Panel Facilities ........................................
6-7
Frequency Information ..........................................
8-9
Accessories ..........................................................
10-11
Specifications ......................................................
12
Warranty and Service ...............................................
13
© 2005 COMTEK® All rights reserved
Printed in U.S.A. 0105BST75
INTRODUCTION
BST-75
Synthesized
Base Station
Transmitter
he BST-75 mini base station transmitter meets the highest
professional standards while offering outstanding value
and the most advanced technology available. This versatile and
innovative transmitter is simple to use, yet it has sophisticated
features such as “Flash Memory” 98-channel programmability
with synthesized manual 10-channel selectable user-switch. Plus
a unique multi-function R.F. indicator detects bad antenna load, RF
presence, coaxial cable short or open condition for quick and easy
trouble-shooting.
The compact design of this transmitter is ideal for multiple transmitter
installations. Up to four transmitters can be installed in one rack
space. Also, it operates in the 72-76 MHz band under FCC Regulation
Part 90. This allows a greater RF power capability (120 mW) for
greater range and reliability than customary FCC Part 15 systems.
The audio processing circuit produces full fidelity frequency response
from 80 Hz to 10 kHz with very low residual F.M. noise and distortion.
To accommodate a greater variety of receivers, the BST-75 can operate
with non-companded receivers or with companded receivers for higher
fidelity sound reproduction with a signal-to-noise ratio of up to 100 dB.
All this is designed into a stylish, compact, all-metal enclosure suitable
for permanent rack-mount installations or for stand-alone portable
applications.
Page 1
OPERATING INSTRUCTIONS
Equipment Placement
If the BST-75 base station is to be rack mounted, a remote antenna must
be used. The base station should be mounted away from equipment
that uses large power transformers to reduce 60 Hz hum possibilities.
Special Note: When using the base station in close proximity to other
audio equipment, ensure that the audio equipment is not susceptible to
RF interference. This can be accomplished by temporarily installing
the base station as per above, and then while the base station is
operating, checking all audio outputs for uncharacteristic noise. If a
problem is found, move the base station or the remote antenna as far as
possible from the affected equipment. Should you continue to have
problems, contact COMTEK’s Technical Support Services for
assistance.
Power Requirements
The BST-75 base station is designed to be powered by 12 volts DC. The
standard barrel type power jack (5.5mm X 2.1mm) is nonpolar and will
accept either plus or minus 12 volt DC on the center pin. The switching
power supply adaptor supplied is
a universal input type that will
accept 100-240 volt, 47-63 Hz
(AP-12V1B). The on/off switch
on the front panel of the base
station transmitter should be
turned to the “off” position
when the power plug is
initially plugged into the
transmitter.
Page 2
OPERATING INSTRUCTIONS
Remote Antenna
When the BST-75 base station transmitter
is to be rack mounted for permanent
installation, a remote antenna must be
used. The RDA-2 1/4 wave remote
dipole antenna (or equivalent) or the
COMTEK “Phase Right Antenna”
PRA-L72 high performance omni antenna
should be used. These antennas must be
placed vertically polarized up to twenty
feet away from the transmitter with the
coaxial cable supplied. The highest
possible antenna placement away from
any metallic objects is best. For high
gain directional yagi type antennas and
specialty antennas, contact COMTEK’s
Technical Support Services.
Integral Screw-in Whip Antenna
If the BST-75 base station transmitter is to be
used outside of the traditional rack-mounted
environment for stand-alone mobile type
applications, the screw-in whip antenna
(TWA-75) should be used. The transmitter
should be placed on a table or platform as
high as possible so the fully extended
whip antenna is at least 24” away from
any metallic objects. The radiated output
power of the transmitter with this whip
antenna will not be as great as the remote
antennas. The BST-75 transmitter should
only be used in the high power setting when
the telescoping whip antenna is used.
Page 3
OPERATING INSTRUCTIONS
Audio Input Connections
The BST-75 base station transmitter uses an XLR-3F connector with a
“Combo” 1/4” phone jack. The XLR portion of the connector will
accept a true balanced or unbalanced line level signal up to +20 dBm.
The 1/4” phone jack portion of the connector is a dedicated input for a
phantom-powered, two-conductor Electret microphone. The
HM-100.25 behind-the-neck
directional boom microphone
is normally used for language
interpretation, but any twoconductor Electret microphone
may be used in this input.
Audio Adjustments
In order to ensure the highest possible transmission fidelity, the
transmitter must be modulating at least 50% with normal speech
(0 dB on the VU meter). This adjustment is made in the following
manner:
a. Ensure that the audio source has been optimized for best
signal-to-noise ratio.
b. The XLR-3 connector located on the back of the transmitter is
used for line level balanced or unbalanced audio source (0 to +20 dBm).
c. Set the AF Gain Control on the back of the base station to fully
counterclockwise and then, while normal program information is
present, slowly rotate the “LEVEL” control clockwise until the VU
meter on the front panel begins to deflect. Adjustment should be made
so that normal speech or music deflects the 0dB yellow LED. Only very
loud speech or music should deflect the VU meter full-scale into the
last red LED.
Page 4
OPERATING INSTRUCTIONS
Audio Processing Circuit
The audio processing system incorporates a peak-level compressor to
prevent over-modulation and reduce audio distortion at high levels.
This compressor has a very fast attack time and a carefully controlled
decay time to optimize the dynamic performance of the audio processing system. (The VU meter will indicate this compressor action when
the red LEDs are illuminated.) The audio is also equalized to add
pre-emphasis as well as a very sharp high frequency roll-off circuit to
minimize high frequency noise in the audio signal. The total frequency
response and performance of the system is, however, determined by the
corresponding de-emphasis and equalization used in the receiver.
In order to accommodate a greater variety of receivers, the BST-75
transmitter incorporates the option to operate with receivers that have
companded or non-companded audio processing. However, the BST-75
transmitter must operate non-companded with non-companded
receivers and companded only with receivers that incorporate
companding processing. A miss-match will result in unacceptable
performance.
Basic Companding Theory
The dynamic range of the audio signal is compressed in the transmitter
at a 2:1 ratio. The receiver then expands the audio signal at a complementary 1:2 ratio to restore the dynamic range of the audio signal to the
original level and also to provide additional noise reduction when no
audio signal is present.
Page 5
BST-75 FRONT PANEL
1 OPTIONAL ANTENNA: Used for mobile type applications.
2 POWER SWITCH: Turns the transmitter on or off.
3 POWER LED INDICATOR: Illuminates when the power is on.
4 VU METER: Displays the audio level being used for modulation.
(See Audio Adjustment Section.)
5 ANTENNA INDICATOR: Detects coaxial cable shorts and open
conditions, bad antenna load, and RF presence.
6 RACK-MOUNTING SCREWS: Used for mounting BST-75 to
rack-mounting panels.
Page 6
BST-75 REAR PANEL
10 11
12
7 DC INPUT JACK: Requires 12 VDC at 200 mA source (Pin-1 ground,
pin-4 +12 volts).
8 TUNING SWITCH: Selects the frequency on which the transmitter will
operate. (See Frequency Information Section.)
9 EXTERNAL ANTENNA JACK: BNC connector provides a standard
50 ohm RF output for use with an external antenna.
10 RF POWER SWITCH: Adjusts the RF power output of the transmitter
(High-120mW, Mid-40mW, Low-10mW).
11 AUDIO LEVEL CONTROL: This control is used to set the proper
modulation level when referenced with the VU meter.
12 MIC / LINE AUDIO INPUT: XLR-3 accepts balanced line level input.
1/4” phone jack accepts 2-conductor electret microphone type only.
Page 7
BST-75 FREQUENCY INFORMATION
USER-SWITCHABLE
SELECTED CHANNELS
(STANDARD PROGRAM)
CHANNEL FREQUENCY
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
72.100 MHz
72.300 MHz
72.500 MHz
72.700 MHz
72.900 MHz
75.500 MHz
75.700 MHz
75.900 MHz
74.710 MHz
75.310 MHz
Channel #1
Frequency Selection
The BST-75 transmitter can
operate on any 10 channels
that have been programmed
from the available 72-76 MHz
frequencies of the Business
Radio Service under FCC
Regulation Part 90. After you
have determined the channels
on which you are going to
operate, position the rotary
switch to indicate that channel.
AVAILABLE 72-76 MHz
“FLASH MEMORY”
PROGRAMMABLE CHANNELS
FREQUENCY
FREQUENCY
FREQUENCY
72.020 MHz
72.040 MHz
72.060 MHz
72.080 MHz
72.100 MHz
72.120 MHz
72.140 MHz
72.160 MHz
72.180 MHz
72.200 MHz
72.220 MHz
72.240 MHz
72.260 MHz
72.280 MHz
72.300 MHz
72.320 MHz
72.340 MHz
72.360 MHz
72.380 MHz
72.400 MHz
72.420 MHz
72.440 MHz
72.460 MHz
72.480 MHz
72.500 MHz
72.520 MHz
72.540 MHz
72.560 MHz
72.580 MHz
72.600 MHz
72.620 MHz
72.640 MHz
72.660 MHz
72.680 MHz
72.700 MHz
72.720 MHz
72.740 MHz
72.760 MHz
72.780 MHz
72.800 MHz
72.820 MHz
72.840 MHz
72.860 MHz
72.880 MHz
72.900 MHz
72.920 MHz
72.940 MHz
72.960 MHz
72.980 MHz
74.610 MHz
74.630 MHz
74.650 MHz
74.670 MHz
74.690 MHz
74.710 MHz
74.730 MHz
74.750 MHz
74.770 MHz
74.790 MHz
75.210 MHz
75.230 MHz
75.250 MHz
75.270 MHz
75.290 MHz
75.310 MHz
75.330 MHz
75.350 MHz
75.370 MHz
75.390 MHz
75.420 MHz
75.440 MHz
75.460 MHz
75.480 MHz
75.500 MHz
75.520 MHz
75.540 MHz
75.560 MHz
75.580 MHz
75.600 MHz
75.620 MHz
75.640 MHz
75.660 MHz
75.680 MHz
75.700 MHz
75.720 MHz
75.740 MHz
75.760 MHz
75.780 MHz
75.800 MHz
75.820 MHz
75.840 MHz
75.860 MHz
75.880 MHz
75.900 MHz
75.920 MHz
75.940 MHz
75.960 MHz
75.980 MHz
Page 8
BST-75 FREQUENCY INFORMATION
Frequency Selection
The BST-75 transmitter comes from the factory on 10 standard
manually selectable channels. Other group frequencies are available
from the 98 “Flash Memory” programmable channel list and have been
coordinated for simultaneous operation. These group frequencies
can be programmed for use with the manual 10-channel selectable
user-switch. Frequency coordination and after-sale programming for
different compatible frequency groups can be done through COMTEK’s
Technical Support Services.
GROUP 1
GROUP 2
GROUP 3
FREQUENCY
FREQUENCY
FREQUENCY
72.020
72.220
72.720
74.610
75.620
75.720
MHz
MHz
MHz
MHz
MHz
MHz
72.080
72.180
72.720
74.770
75.580
75.920
MHz
MHz
MHz
MHz
MHz
MHz
72.260
72.580
72.790
74.250
75.840
75.960
MHz
MHz
MHz
MHz
MHz
MHz
Multiple Channel Operation
When multiple transmitters (more than two) are used in the same
proximity, intermodulation interference often occurs. This condition is
common to all radio receivers to some extent when multiple transmitters
are used in the same operating area. The RF signals will “MIX”
together generating additional signals. If these product frequencies are
too close to a frequency to which the receiver can also respond, you
will experience intermodulation interference which may cause
undesirable operation.
To avoid this type of self-interference when multiple transmitters
are used in the same proximity, transmitting frequencies must be
coordinated by selecting from frequencies in the same group.
Page 9
BST-75 ACCESSORIES
Included Accessories
1. C-16 Carrying case
2. BST-75 Operator’s manual
3. TWA-75 Telescoping
whip antenna
4. AP-12V1B Power adaptor
(115 VAC Input)
5. BST-75 Base station transmitter
Page 10
BST-75 ACCESSORIES
Optional Accessories
1. RDA-2B Remote
dipole antenna
2. PRA Phase-Right
coaxial antenna
3. PRA Phase-Right
antenna mount
4. HM-100.25 Behind-the-neck
directional boom microphone
5. RMK 75-4 Quad
rack-mount face plate
6. RMK 75-2 Double
rack-mount face plate
7. RMK 75 Single
rack-mount face plate
Page 11
BST-75 SPECIFICATIONS
Audio Inputs:
• Line level balanced input
0 dBm for 80% modulation
(+20 dBm max)
• Electret mic unbalanced input
-25 dBV at 5 k for 80% modulation
Modulation Limiter:
Peak compressor type with
high linear overload protection
(25 dB). Attack time less than
1 ms, recovery time 10 ms
Audio Processing:
Companded and non-companded
to accommodate a variety of
receivers
Connectors:
• XLR-3F Combo with 1/4”
phone jack
• Barrel type 5.5mm X 2.1mm
DC power jack
• BNC type RF output
Audio Gain Control:
Limited to 20 dB
Frequency Modulation:
10 kHz deviation
Operation Indicators:
• LED bargraph VU meter
• LED antenna load and coaxial
cable condition indicator
• LED DC power indicator
RF Output Power:
Maximum power output for
FCC Part 90 (120mV)
Antenna:
• 19” Telescopic antenna mounts
directly into top of transmitter
• BNC RF output connector for
optional external antenna
Frequency Stability:
Better than 0.002% digitally
synthesized, crystal controlled
Operating Frequency:
72.020 to 75.980 MHz
(98 channels)
FCC Compliance:
Type Accepted under FCC
Part 90
Harmonic and Spurious Emissions:
Better than 50 dB below carrier
Power Requirements:
12 Volts DC, 200 mA max
Dimensions:
3 3/4" X 1 5/8" X 5 1/4" deep
Frequency Response:
80 Hz to 10 kHz
Weight:
Audio Distortion:
Less than 0.5% at 80% modulation
15 1/4 oz.
NOTE: Specifications subject to
change without notice
Page 12
WARRANTY
COMTEK warrants this product to be free from defects in workmanship and
material under normal use and conditions for a period of one year from date
of original purchase. Items such as batteries, neckloops, and cords are not
covered by the warranty. Damage due to misuse, ill treatment and
unauthorized modification and repairs are not covered by this warranty.
COMTEK is not liable for consequential damages arising out of any failure
of the equipment to perform as intended. COMTEK shall bear no responsibility
or obligation with respect to the manner of use of any equipment sold by it.
COMTEK SPECIFICALLY DISCLAIMS AND NEGATES ANY WARRANTY OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
OF SUCH EQUIPMENT INCLUDING, WITHOUT LIMITATION, ANY
WARRANTY THAT THE USE OF SUCH EQUIPMENT FOR ANY PURPOSE
WILL COMPLY WITH APPLICABLE LAWS AND REGULATIONS.
Service Policies
Warranty repairs must be done by COMTEK. Only factory technicians are
authorized to perform warranty service on the BST-75 transmitter. Before
returning the BST-75 for service, a Return Authorization Number should
be obtained from the service department by calling 1-800-496-3463 or
1-801-466-3463. Return the unit to the factory with the original or comparable
packing. COMTEK will pay for insurance and ground return shipping costs in
the United States for all warranty service.
357 West 2700 South • Salt Lake City, Utah 84115
Phone: (800) 496-3463 • Fax: (801) 484-6906
Web: www.comtek.com
E-mail: sales@comtek.com
357 West 2700 South • Salt Lake City, Utah 84115 • Phone: (800) 496-3463 • Fax: (801) 484-6906 • www.comtek.com

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