BST-25 / TV 5-6 OPERATOR’S MANUAL (76-88 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
INTRODUCTION
BST-25 / TV 5-6
Synthesized
Base Station
Transmitter
he BST-25 is a low power auxiliary base station transmitter
T
designed to operate under Part 74 of the FCC Regulations in the
unused TV channel 5 and TV channel 6 spectrum (76.2 to 87.8 MHz).
This transmitter, along with a personal receiver, is used in a TV
production studio for IFB and talent cueing. It may also be used on
remote location from an ENG truck for the same application.
In motion picture production, the BST-25 is used as a low power
auxiliary base station transmitter located on site with the sound
recording equipment. Directors, boom-operators, and others may
receive, with a personal receiver and headphone, the high fidelity
transmission from the BST-25 to monitor sound track audio being
recorded. This transmission, or “Confidence Channel”, may also
be used as an IFB for talent or crew members.
Page 1
OPERATING INSTRUCTIONS
Equipment Placement
If the BST-25 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.
If the base station is to be used outside of a traditional rackmounted environment, the screw-in whip antenna should be
free of any metallic objects when fully extended.
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 application engineering department for
assistance.
Remote Antenna
When the base station is rack-mounted or when greater system
range is required, a remote antenna should be used. For
vehicle installation, a 1/4 wave roof-mount (MO-1/4 wave
or MAG-1/4 wave) should be used. For field or studio
applications, the COMTEK “Phase Right Antenna”
(PRA-L TV 5-6) is an easy-to-use, high performance, omni
antenna. For high gain directional yagi type antennas and
custom antennas, contact COMTEK’s application engineering
department for assistance.
Please note: Do not install screw-in whip antenna if remote
antenna is used.
Page 2
Power Requirements
The BST-25 base station is designed to be powered by 12 volts
DC. A power adaptor is furnished for use with standard 110V
AC. The on/off switch on the front panel of the base station
turns on the transmitter.
Audio Input Connections
The base station transmitter has facilities for audio input from
a mic, line, or speaker level source. The mic/line level audio
input is a transformer balanced input and requires a standard
XLR-3 male connector. Unbalanced input is accomplished by
shorting pin-3 to pin-1 (audio ground), leaving pin-2 as the
audio source. Please note: when unbalanced input is used, it is
recommended that all audio input cables be kept as short as
possible.
Set-up
a. Select an appropriate location for the base station in
accordance with “Equipment Placement” instructions.
b. Set the “MIC/LINE” switch, located on the back of the
base station transmitter, to the appropriate position: "MIC"
position for low impedance microphones or “LINE” position
for line level feed.
c. Connect the audio source or microphone to the
base station using the appropriate input. Be sure to set the
audio input level adjustment on the base station to its
full counterclockwise position.
Page 3
OPERATING INSTRUCTIONS (continued)
d. Plug the adaptor into a standard AC outlet and plug the
power connector into the DC input jack of the transmitter.
Turn the display switch on the front of the transmitter "ON"
to allow monitoring of the transmitter frequency. Turn the
main power switch on the front of the base station to the "ON"
position. The front display should now be illuminated.
e. Mount the telescoping whip antenna in the hole on
top of the base station rotating it clockwise until it is firmly
seated. Extend the antenna completely. During normal
operation the antenna indicator should not flash. Turn on
the transmitter and verify that the antenna indicator is not
flashing. If the antenna indicator is flashing, shorten the
telescoping whip antenna by 2 inches and again check the
indicator. Continue this procedure until the indicator
remains off. If you experience trouble, please contact
COMTEK's application engineering department for
assistance. If you are using an external type antenna, DO
NOT install the telescoping antenna. Instead, connect the
coaxial feed line for the external antenna to the external
antenna port on the back of the BST-25.
Note:
For optimum performance when using the telescoping
whip antenna, the transmitter should be placed on a large
metallic surface. Adjustment of antenna length for a “No
Flash” condition on antenna indicator will ensure maximum
radiation.
Page 4
Audio Adjustments
In order to ensure the highest possible transmission fidelity,
the transmitter must be modulating at least 50% with normal
speech (-3 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 “MIC/LINE” switch located at the back of the
transmitter should be switched to the appropriate setting:
"MIC" for mic level or weak line level input; “LINE” level for
line level input.
c. The “LEVEL” control on the back of the base station
should be set 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 meter mid-scale. Only very loud
speech or music should deflect the VU meter full-scale.
Frequency Selection
The BST-25 base station transmitter
has the ability to operate on one of 119 preset channels
between 76.200 MHz and 87.800 MHz (TV channel 5 and TV
channel 6). Channels are designated by both frequency and
channel number. Channels which operate in the TV 5
spectrum are prefixed with a 5 (5-50 is 81.100 MHz),
channels operating in the TV 6 spectrum are prefixed with
a 6 (6-50 is 87.100 MHz). This channel rastering makes it easy
to determine which TV band you are operating on.
Page 5
IMPORT ANT
OPERATING INSTRUCTIONS (continued)
If you are using this transmitter in a area which does not have a
TV station operating on channel 5, you can use one of the channels
in the TV 5 range. Conversely, if the area does not have a station
on TV 6, you can operate on one of the TV 6 channels. Note: It is
unlawful to operate this transmitter in a band that is already
occupied by a TV station. After you have determined the channel
on which you are going to operate, use the “TUNING” button to
select the channel that you have chosen. See charts on pages 10
and 11 for preset selectable frequencies.
Multiple Channel Operation
Simultaneous operation of more than two channels requires
coordination of the frequencies that are used to avoid
intermodulation interference. To avoid this type of interference,
select frequencies from one of the standard groups (see frequency
group charts on page 11), or use COMTEK’s frequency selection
guide software to determine appropriate frequencies.
Contact COMTEK to obtain a free copy of the frequency
selection software or download it off the web at
www.comtek.com/frequency.html
Test Tone
The BST-25 base station transmitter has an internal 400 Hz source
which is transmitted when the “TONE” switch is enabled.
This source is intended to be used to make technical adjustments
and to verify the operation of the system. Under normal
operation the “TONE” switch should be disabled.
Page 6
Speech EQ
On the back of the transmitter there is a switch labeled “EQ”. With this
function enabled (switch up), the audio dynamics and frequency
response are processed to improve intelligibility of speech. If the
primary audio source is going to be speech, you should enable this
processing! If the main audio source is going to include music
information, you should disable it. You may want to experiment to
determine which position sounds most pleasing with the program
source you intend to use.
Display On and Off
The digital display can be turned on or off using the “DISPLAY”
switch. Disabling the display reduces the current consumption of the
transmitter for battery operation. In environments where the display
could be distracting, disabling the display may also be appropriate.
When the display is disabled, the tuning controls are also disabled,
ensuring the transmitter frequency is not changed inadvertently. With
the display disabled, one segment is turned on as a power indicator.
Additionally, the “LOCK OUT” indicator is illuminated indicating the
tuning is disabled. The VU meter and the “ANTENNA” indicator are
unaffected.
Lock Out
After the transmitting frequency has been determined, the transmitter
tuning function can be disabled with the “LOCK OUT” switch on the
back of the transmitter. This ensures that the transmitter operating
frequency is not inadvertently changed. The “LOCK OUT” indicator
(above the first numeric digit on the display) will illuminate indicating
that the tuning has been disabled. When rack-mounting the transmitter,
this switch must be accessed from behind the rack. This provides
added protection from tampering.
Page 7
BST-25 FRONT PANEL
3
2
1
1
DISPLAY SWITCH: This switch disables the digital display to conserve
4
current when used with a battery.
5 6
7
8
9
2
TONE SWITCH: Enables/disables the internal 400 Hz test tone.
3
TUNING SWITCH: Selects the frequency on which the transmitter will
operate.
4
LOCK OUT INDICA TOR: Illuminates when the “TUNING” switch is
disabled by setting the “LOCK OUT” switch (rear panel) to “ON”.
5
DIGITAL FREQUENCY DISPLAY: Displays the frequency on which the
transmitter is operating.
6
ANTENNA INDICATOR: Flashes when the transmitter senses a deficient
antenna condition.
7
VU METER: Displays the level of audio being transmitted. Used to
adjust the “LEVEL” (rear panel) control.
8
DIGITAL CHANNEL DISPLA Y: Displays the channel on which the
transmitter is operating.
9
POWER SWITCH: Turns the transmitter on or off.
Page 8
BST-25 REAR PANEL
10
10
LOCK OUT SWITCH: Disables the front panel “TUNING” switch,
11 12 13 14 15
16
locking the transmitter on one frequency.
11
DC INPUT JACK: Requires 12 VDC at 500 mA source (Pin-1 ground,
pin-4 +12 volts).
12
EXTERNAL ANTENNA JACK: BNC connector provides a standard 50
ohm RF output for use with an external antenna.
13
SPEECH ENHANCEMENT SWITCH: Enables and disables speech
enhance feature. Enable this function (switch up) for speech, and disable
it (switch down) for music.
14
LEVEL CONTROL: This control should be adjusted so that normal
audio deflects the VU meter to midscale.
BALANCED AUDIO INPUT: Accepts audio from a line level or mic level.
15
For XLR3 or 1/4” TRS phone plug.
16
MIC/LINE SWITCH: Selects the desired audio input sensitivity.
Page 9
BST-25
TV CHANNEL 5
FREQUENCY CHART
CHANNEL
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
FREQUENCY
76.200 MHz
76.300 MHz
76.400 MHz
76.500 MHz
76.600 MHz
76.700 MHz
76.800 MHz
76.900 MHz
77.000 MHz
77.100 MHz
77.200 MHz
77.300 MHz
77.400 MHz
77.500 MHz
CHANNEL FREQUENCY
5-31
5-32
5-33
5-34
5-35
5-36
5-37
5-38
5-39
5-40
5-41
5-42
5-43
5-44
79.200 MHz
79.300 MHz
79.400 MHz
79.500 MHz
79.600 MHz
79.700 MHz
79.800 MHz
79.900 MHz
80.000 MHz
80.100 MHz
80.200 MHz
80.300 MHz
80.400 MHz
80.500 MHz
5-15
5-16
5-17
5-18
5-19
5-20
5-21
5-22
5-23
5-24
5-25
5-26
5-27
5-28
5-29
77.600 MHz
77.700 MHz
77.800 MHz
77.900 MHz
78.000 MHz
78.100 MHz
78.200 MHz
78.300 MHz
78.400 MHz
78.500 MHz
78.600 MHz
78.700 MHz
78.800 MHz
78.900 MHz
79.000 MHz
5-45
5-46
5-47
5-48
5-49
5-50
5-51
5-52
5-53
5-54
5-55
5-56
5-57
5-58
5-59
80.600 MHz
80.700 MHz
80.800 MHz
80.900 MHz
81.000 MHz
81.100 MHz
81.200 MHz
81.300 MHz
81.400 MHz
81.500 MHz
81.600 MHz
81.700 MHz
81.800 MHz
81.900 MHz
82.000 MHz
5-30
79.100 MHz
Page 10
TV 5 Audio
81.750 MHz
BST-25
TV CHANNEL 6
FREQUENCY CHART
CHANNEL FREQUENCY
6-0
6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8
6-9
6-10
6-11
6-12
6-13
82.100 MHz
82.200 MHz
82.300 MHz
82.400 MHz
82.500 MHz
82.600 MHz
82.700 MHz
82.800 MHz
82.900 MHz
83.000 MHz
83.100 MHz
83.200 MHz
83.300 MHz
83.400 MHz
CHANNEL
6-30
6-31
6-32
6-33
6-34
6-35
6-36
6-37
6-38
6-39
6-40
6-41
6-42
6-43
FREQUENCY
85.100 MHz
85.200 MHz
85.300 MHz
85.400 MHz
85.500 MHz
85.600 MHz
85.700 MHz
85.800 MHz
85.900 MHz
86.000 MHz
86.100 MHz
86.200 MHz
86.300 MHz
86.400 MHz
6-14
6-15
6-16
6-17
6-18
6-19
6-20
6-21
6-22
6-23
6-24
6-25
6-26
6-27
6-28
83.500 MHz
83.600 MHz
83.700 MHz
83.800 MHz
83.900 MHz
84.000 MHz
84.100 MHz
84.200 MHz
84.300 MHz
84.400 MHz
84.500 MHz
84.600 MHz
84.700 MHz
84.800 MHz
84.900 MHz
6-44
6-45
6-46
6-47
6-48
6-49
6-50
6-51
6-52
6-53
WIDE-BAND CHANNELS
(for use with FM tunable receivers)
6-54
6-55
6-56
6-57
86.500 MHz
86.600 MHz
86.700 MHz
86.800 MHz
86.900 MHz
87.000 MHz
87.100 MHz
87.200 MHz
87.300 MHz
87.400 MHz
87.500 MHz
87.600 MHz
87.700 MHz
87.800 MHz
6-29
85.000 MHz
Page 11
TV 6 Audio
87.750 MHz
BST-25
TV CHANNEL 5
FREQUENCY GROUPS
BST-25
TV CHANNEL 6
FREQUENCY GROUPS
GROUP ONE
CHANNEL FREQUENCY
5-3
5-6
5-10
5-15
5-21
5-34
5-42
5-56
GROUP TWO
CHANNEL FREQUENCY
5-5
5-7
5-13
76.400 MHz
76.700 MHz
77.100 MHz
77.600 MHz
78.200 MHz
79.500 MHz
80.300 MHz
81.700 MHz
76.600 MHz
76.800 MHz
77.400 MHz
GROUP ONE
CHANNEL FREQUENCY
6-4
6-7
6-9
6-13
6-20
6-30
6-38
6-50
GROUP TWO
CHANNEL FREQUENCY
6-2
6-5
6-28
82.500 MHz
82.800 MHz
83.000 MHz
83.400 MHz
84.100 MHz
85.100 MHz
85.900 MHz
87.100 MHz
82.300 MHz
82.600 MHz
84.900 MHz
5-33
5-38
5-47
5-54
5-57
GROUP THREE
CHANNEL FREQUENCY
5-2
5-8
5-11
5-16
5-18
5-29
5-41
5-58
79.400 MHz
79.900 MHz
80.800 MHz
81.500 MHz
81.800 MHz
76.300 MHz
76.900 MHz
77.200 MHz
77.700 MHz
77.900 MHz
79.000 MHz
80.200 MHz
81.900 MHz
6-34
6-42
6-44
6-49
6-53
GROUP THREE
CHANNEL FREQUENCY
6-1
6-3
6-6
6-10
6-16
6-24
6-36
6-52
85.500 MHz
86.300 MHz
86.500 MHz
87.000 MHz
87.400 MHz
82.200 MHz
82.400 MHz
82.700 MHz
83.100 MHz
83.700 MHz
84.500 MHz
85.700 MHz
87.300 MHz
Page 12
BST-25 INTERNAL ADJUSTMENTS
NOTE: The COMPAND switch must be set to the OFF position for use with
“Walkman” FM band type receivers and TV monitors. Must be set to the
position for use with PR-25 and PR-216/TV 5-6 receivers.
ON
Page 13
BST-25 ACCESSORIES
Included Accessories
1. C-16 Carrying case
2. BST-25 Operator’s manual
3. TWA-72 Whip antenna
4. BST-25 Base station transmitter
5. AP-12V1 Power adaptor
(115 VAC Input)
Page 14
BST-25 ACCESSORIES
Optional Accessories
1. RDA-2 Remote
dipole antenna
2. PRA-5/6 Phase-Right
antenna
3. MO-1/4 wave vehicle
installation antenna or
MO-1/4 wave magnetic
mount antenna
4. PRA-B Phase-Right
wall mounting bracket
5. RMK 25 Single
rack-mount face plate
6. RMK 25-2 Double
rack-mount face plate
Page 15
BST-25 / TV 5-6 SPECIFICATIONS
Audio Inputs:
•
Mic XLR, 600 ohm balanced -40
dBV (nominal)
•
Line XLR, 10 k ohm balanced 0
dBV (nominal)
Connectors:
•
XLR-3 Female audio input
connector for mic and line input
•
XLR-4 Male power input 12
volts
•
BNC type RF output connector
Operation Indicators:
LED Bargraph VU Meter
•
displays audio input (modulation)
Two-Digit Alpha Numeric Display
•
shows operating channel
Five-Digit Numeric Display
•
shows operating frequency
Antenna Indicator displays
•
deficient antenna condition
Lock Out Indicator shows
•
tuning has been disabled
Antenna:
Telescopic antenna mounts
•
directly into top of transmitter
BNC RF output connector for
•
optional external antenna
FCC Compliance:
Type Accepted under Part 74
Audio Distortion:
Less than 0.5% at 80% modulation
Modulation Limiter:
Soft compressor type with high
(25 dB) linear overload protection,
attack time less than 1 ms,
recovery time 10 ms
Audio Gain Control:
Greater than 40 dB
Test Tone Generator:
400 Hz 0.05% distortion
Frequency Modulation:
•10 kHz deviation for narrow
band channels,
•75 kHz deviation for wide
band channels
RF Output Power:
Set for 50 mW for FCC Part 74
Frequency Stability:
Better than 0.002%. digitally
synthesized, crystal controlled
Operating Frequency:
76.2 to 87.8 MHz
Harmonic and Spurious
Emissions:
Better than 55 dB below carrier
Power Requirements:
12 Volts DC, 300 mA max
Frequency Response:
80 Hz to 15 kHz
Dimensions:
6 1/2" wide x 1 3/4" high x 5 5/8"
deep
Weight:
44 oz.
NOTE: Specifications subject to change without
notice.
Page 16
WARRANTY AND SERVICE
Warranty
COMTEK transmitters and receivers are warranted to be free from defects in
workmanship and material under normal stand-alone use and conditions for a
period of
earphones, neckloops, and cords are warranted to be free from defects in
workmanship and material for a period of 90 days from the date of original
purchase. Batteries are not covered by this warranty. Damage due to abnormal
use, extreme conditions, misuse, use of the product as a component of another
product, ill treatment and unauthorized modification and repairs are not
covered by this warranty. COMTEK is not liable for any consequential or
punitive 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 OF THE PRODUCT FOR A PARTICULAR PURPOSE
INCLUDING, WITHOUT LIMITATION, ANY WARRANTY THAT THE USE
OF SUCH EQUIPMENT FOR ANY PURPOSE WILL COMPLY WITH
APPLICABLE LAWS AND REGULATIONS.
two years from date of original purchase. Items such as headphones,
Service Policy
Warranty repairs must be done by COMTEK. Only factory technicians are
authorized to perform warranty service on the BST-25 transmitter. Before
returning the BST-25 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 • www.comtek.com
E-mail: sales@comtek.com
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