BST-50b 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.
INTRODUCTION BST-50b Synthesized Base Station Transmitter T he BST-50b is a high fidelity, professional quality, base station 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.
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.
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.
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.
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.
OPERATING INSTRUCTIONS (continued) Multiple Channel Operation Simultaneous operation with more than two channels requires coordination of the frequencies that are used to avoid interference. This interference would result in poor or unusable performance. When multiple transmitters are broadcasting, the RF signals will “mix” together generating additional signals on other frequencies in the receiver’s mixer. This condition, common to all RF receivers, is called intermodulation or intermod.
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 or other program information, you should disable it.
BST-50b FRONT PANEL 1 2 3 4 5 6 7 8 9 1 DISPLAY SWITCH: This switch disables the digital display to conserve current when used with a battery. 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 INDICATOR: Illuminates when the “TUNING” switch is disabled by setting the “LOCK OUT” switch (rear panel) to “ON”.
BST-50b REAR PANEL 10 11 12 13 14 15 16 10 LOCK OUT SWITCH: Disables the front panel “TUNING” switch, 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.
BST-50b FREQUENCY CHART CHAN FREQ CHAN FREQ CHAN FREQ 01 72.020 MHz 31 72.720 MHz 61 75.330 MHz 02 72.040 MHz 32 72.740 MHz 62 75.350 MHz 03 72.060 MHz 33 72.760 MHz 63 75.370 MHz 04 72.080 MHz 34 72.780 MHz 64 75.390 MHz 05 72.100 MHz 35 72.800 MHz 65 75.420 MHz 06 72.120 MHz 36 72.820 MHz 66 75.460 MHz 07 72.140 MHz 37 72.840 MHz 67 75.500 MHz 08 72.160 MHz 38 72.860 MHz 68 75.540 MHz 09 72.180 MHz 39 72.880 MHz 69 75.580 MHz 10 72.
BST-50b FREQUENCY GROUPS For Non-Companded Operation 1:1 With PR-72b and PR-75 CHANNEL FREQUENCY A B C D E F G H I J 72.100 MHz 72.300 MHz 72.500 MHz 72.700 MHz 72.900 MHz 75.500 MHz 75.700 MHz 75.900 MHz 74.700 MHz 75.300 MHz Companded Operation Only 2:1 With PR-25 and PR-216 GROUP ONE FREQUENCY A B C D E F G H I J 72.100 MHz 72.300 MHz 72.500 MHz 72.700 MHz 72.900 MHz 75.500 MHz 75.700 MHz 75.900 MHz 74.700 MHz 75.300 MHz FREQUENCY 01 11 31 45 70 75 72.020 MHz 72.220 MHz 72.720 MHz 74.
BST-50b 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-2 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 cond
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 two years from date of original purchase. Items such as headphones, 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.
