COMTEK BST-50b User Manual

BST-50b OPERATOR’S MANUAL (72-76 MHz)

Synthesized
Base Station
Transmitter

357 West 2700 South • Salt Lake City, Utah 84115 • Phone: [phone] • Fax: [phone] • www.comtek.com

INTRODUCTION

BST-50b

Synthesized
Base Station
Transmitter

he BST-50b is a high fidelity, professional quality, base station

T

transmitter designed for assistive listening, language
translation, and remote monitoring applications. This transmitter
operates under F.C.C. Part 90 in the business band which allows
for higher power ideal for large area venues such as stadiums,
coliseums, and auditoriums. The BST-50b transmits on a
user-selectable channel in the 72-76 MHz band to a variety
of COMTEK personal receivers.

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OPERATING INSTRUCTIONS

Equipment Placement

The base station should be placed on top of an equipment
rack, control console table, or special shelf where the pull-out
whip antenna will be free of any metallic objects when fully
extended.

If the base station is to be rack-mounted, it should be
mounted away from equipment that uses large power
transformers to reduce 60 Hz hum possibilities.

Special Note:

When using the BST-50b in close proximity to other audio
equipment, ensure that the audio equipment is not susceptible
to RF interference, i.e. hum, oscillations, etc. This can be
accomplished by temporarily installing the BST-50b as per
above and then, while the BST-50b is operating, checking all
audio outputs for uncharacteristic noise. If a problem is
found, move the BST-50b 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.

IMPORTANT

Remote Antenna

When the BST-50b base station is rack-mounted or when
greater system range is required, a remote antenna should be
used. The BST-50b base station transmitter has a 50 ohm
BNC antenna port which mates with a number of
standard external antennas including the Phase Right
antenna (model PRA-L 72-76 MHz). The antenna should be
mounted away from any metallic objects and away from

the equipment rack.

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Power Requirements

The 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 true balanced input and requires a standard XLR-3
male connector. Unbalanced input is accomplished by
shorting pin-2 to pin-1 (audio ground), leaving pin-3 as the
audio source. Please note that it is recommended that all audio

input cables be kept as short as possible.

Set-up

a. Select an appropriate location for the BST-50b, i.e. a
sound cabinet or closet, where there is easy access to the
audio equipment and where the antenna can be extended to
the correct length.

b. Set the “MIC/LINE” switch, located on the back of the
BST-50b transmitter, to the appropriate position: "MIC"
position for low impedance microphones or “LINE” position
for line level feed from a mixer.

c. Connect the audio source or microphone to the BST-50b
using the appropriate input. Be sure to set the audio input
level adjust on the BST-50b to its full counter-clockwise
position.

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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 BST-50b to the "ON" position. The front display
should now be illuminated.

e. Mount the telescoping whip antenna in the hole on
top of the BST-50b, 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-50b.

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 insure
maximum radiation.

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