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.
TABLE OF CONTENTS Introduction ........................................................... 1 Equipment Placement ............................................... 2 Power Requirements ....................................................... 2 Remote Antenna ...................................................... 3 Screw-in Whip Antenna ............................................ 3 Audio Input Connections ............................................... 4 Audio Adjustments ...........................
INTRODUCTION BST-75 Synthesized Base Station Transmitter T 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.
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.
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.
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.
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.
BST-75 FRONT PANEL 1 2 3 4 5 6 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.
BST-75 REAR PANEL 7 8 9 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).
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.
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.
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 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.
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.
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.
357 West 2700 South • Salt Lake City, Utah 84115 • Phone: (800) 496-3463 • Fax: (801) 484-6906 • www.comtek.