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-2B 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 object is best.
OPERATING INSTRUCTIONS Audio Input Connections The BST 75-216 base station transmitter uses an XLR-3F connector with a “Combo” 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” mono jack portion of the connector can be used for AUX level audio or line level audio up to +5 dBm. It also can be used to directly phantom-power most two-conductor electret headset microphones.
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: Flashes when transmitter detects coaxial cable shorts and open conditions, bad antenna load. 6 RACK-MOUNTING SCREWS: Used for mounting BST-75 to rack-mounting panels.
BST-75 REAR PANEL 7 8 9 10 11 12 7 POWER INPUT JACK: Requires 12V AC at 200 mA. Will also accept 12V DC with either positive or negative center pin (for field operation only). 8 CHANNEL SELECTOR 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.
BST-75 FREQUENCY INFORMATION AVAILABLE 72-76 MHz “FLASH MEMORY” COMPANDED CHANNELS USER-SWITCHABLE STANDARD CHANNELS NON-COMPANDED CHANNEL FREQUENCY A B C D E F G H I J #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 72.1 72.3 72.5 72.7 72.9 75.5 75.7 75.9 74.7 75.3 MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz GROUP FREQUENCY CHART GROUP 1 CHANNEL FREQUENCY A E H J #1 #5 #8 #10 72.1 72.9 75.9 75.3 MHz MHz MHz MHz GROUP FREQUENCY CHART GROUP 2 CHANNEL FREQUENCY B #2 G #7 I #9 72.3 MHz 75.7 MHz 74.
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 88 “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-75 Carrying case 2. BST-75 Operator’s manual 3. TWA-75 Telescoping whip antenna 4. AP-12VAC Power adaptor (115V AC 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 1/4” 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, XLR-3F) • Unbalanced input (+5 dBm Max) or two wire electret microphone with bias voltage for electret microphone (-35 dBv at 5 K ohms) with 1/4” phone jack. Connectors: • XLR-3F Combo with 1/4” phone jack • Barrel type 5.5mm X 2.1mm power jack AC or DC • BNC type RF output Modulation Limiter: Peak compressor type with high linear overload protection (25 dB).
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.
357 West 2700 South • Salt Lake City, Utah 84115 • Phone: (800) 496-3463 • Fax: (801) 484-6906 • www.comtek.
