Comtek Communications Technology BST75 Transmitter User Manual Drawing dwg
Comtek Communications Technology Inc Transmitter Drawing dwg
USERS MANUAL
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.com TABLE OF CONTENTS Introduction ........................................................... Equipment Placement ............................................... Power Requirements ....................................................... Remote Antenna ...................................................... Screw-in Whip Antenna ............................................ Audio Input Connections ............................................... Audio Adjustments ............................................... Audio Processing Circuit .......................................... Front and Rear Panel Facilities ........................................ 6-7 Frequency Information .......................................... 8-9 Accessories .......................................................... 10-11 Specifications ...................................................... 12 Warranty and Service ............................................... 13 © 2005 COMTEK® All rights reserved Printed in U.S.A. 0105BST75 INTRODUCTION BST-75 Synthesized Base Station Transmitter 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. indicator detects bad antenna load, RF presence, coaxial cable short or open condition for quick and easy trouble-shooting. The compact design of this transmitter is ideal for multiple transmitter installations. Up to four transmitters can be installed in one rack space. Also, it operates in the 72-76 MHz band under FCC Regulation Part 90. This allows a greater RF power capability (120 mW) for greater range and reliability than customary FCC Part 15 systems. The audio processing circuit produces full fidelity frequency response from 80 Hz to 10 kHz with very low residual F.M. noise and distortion. To accommodate a greater variety of receivers, the BST-75 can operate with non-companded receivers or with companded receivers for higher fidelity sound reproduction with a signal-to-noise ratio of up to 100 dB. All this is designed into a stylish, compact, all-metal enclosure suitable for permanent rack-mount installations or for stand-alone portable applications. Page 1 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. 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 Technical Support Services for assistance. Power Requirements The BST-75 base station is designed to be powered by 12 volts DC. The standard barrel type power jack (5.5mm X 2.1mm) is nonpolar and will accept either plus or minus 12 volt DC on the center pin. The switching power supply adaptor supplied is a universal input type that will accept 100-240 volt, 47-63 Hz (AP-12V1B). The on/off switch on the front panel of the base station transmitter should be turned to the “off” position when the power plug is initially plugged into the transmitter. Page 2 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. The highest possible antenna placement away from any metallic objects is best. For high gain directional yagi type antennas and specialty antennas, contact COMTEK’s Technical Support Services. Integral Screw-in Whip Antenna If the BST-75 base station transmitter is to be used outside of the traditional rack-mounted environment for stand-alone mobile type applications, the screw-in whip antenna (TWA-75) should be used. The transmitter should be placed on a table or platform as high as possible so the fully extended whip antenna is at least 24” away from any metallic objects. The radiated output power of the transmitter with this whip antenna will not be as great as the remote antennas. The BST-75 transmitter should only be used in the high power setting when the telescoping whip antenna is used. Page 3 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-100.25 behind-the-neck directional boom microphone is normally used for language interpretation, but any twoconductor Electret microphone may be used in this input. Audio Adjustments In order to ensure the highest possible transmission fidelity, the transmitter must be modulating at least 50% with normal speech (0 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 XLR-3 connector located on the back of the transmitter is used for line level balanced or unbalanced audio source (0 to +20 dBm). c. Set the AF Gain Control on the back of the base station to 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 0dB yellow LED. Only very loud speech or music should deflect the VU meter full-scale into the last red LED. Page 4 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.) The audio is also equalized to add pre-emphasis as well as a very sharp high frequency roll-off circuit to minimize high frequency noise in the audio signal. The total frequency response and performance of the system is, however, determined by the corresponding de-emphasis and equalization used in the receiver. In order to accommodate a greater variety of receivers, the BST-75 transmitter incorporates the option to operate with receivers that have companded or non-companded audio processing. However, the BST-75 transmitter must operate non-companded with non-companded receivers and companded only with receivers that incorporate companding processing. A miss-match will result in unacceptable performance. Basic Companding Theory The dynamic range of the audio signal is compressed in the transmitter at a 2:1 ratio. The receiver then expands the audio signal at a complementary 1:2 ratio to restore the dynamic range of the audio signal to the original level and also to provide additional noise reduction when no audio signal is present. Page 5 BST-75 FRONT PANEL 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. Page 6 BST-75 REAR PANEL 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). 11 AUDIO LEVEL CONTROL: This control is used to set the proper modulation level when referenced with the VU meter. 12 MIC / LINE AUDIO INPUT: XLR-3 accepts balanced line level input. 1/4” phone jack accepts 2-conductor electret microphone type only. Page 7 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. After you have determined the channels on which you are going to operate, position the rotary switch to indicate that channel. AVAILABLE 72-76 MHz “FLASH MEMORY” PROGRAMMABLE CHANNELS FREQUENCY FREQUENCY FREQUENCY 72.020 MHz 72.040 MHz 72.060 MHz 72.080 MHz 72.100 MHz 72.120 MHz 72.140 MHz 72.160 MHz 72.180 MHz 72.200 MHz 72.220 MHz 72.240 MHz 72.260 MHz 72.280 MHz 72.300 MHz 72.320 MHz 72.340 MHz 72.360 MHz 72.380 MHz 72.400 MHz 72.420 MHz 72.440 MHz 72.460 MHz 72.480 MHz 72.500 MHz 72.520 MHz 72.540 MHz 72.560 MHz 72.580 MHz 72.600 MHz 72.620 MHz 72.640 MHz 72.660 MHz 72.680 MHz 72.700 MHz 72.720 MHz 72.740 MHz 72.760 MHz 72.780 MHz 72.800 MHz 72.820 MHz 72.840 MHz 72.860 MHz 72.880 MHz 72.900 MHz 72.920 MHz 72.940 MHz 72.960 MHz 72.980 MHz 74.610 MHz 74.630 MHz 74.650 MHz 74.670 MHz 74.690 MHz 74.710 MHz 74.730 MHz 74.750 MHz 74.770 MHz 74.790 MHz 75.210 MHz 75.230 MHz 75.250 MHz 75.270 MHz 75.290 MHz 75.310 MHz 75.330 MHz 75.350 MHz 75.370 MHz 75.390 MHz 75.420 MHz 75.440 MHz 75.460 MHz 75.480 MHz 75.500 MHz 75.520 MHz 75.540 MHz 75.560 MHz 75.580 MHz 75.600 MHz 75.620 MHz 75.640 MHz 75.660 MHz 75.680 MHz 75.700 MHz 75.720 MHz 75.740 MHz 75.760 MHz 75.780 MHz 75.800 MHz 75.820 MHz 75.840 MHz 75.860 MHz 75.880 MHz 75.900 MHz 75.920 MHz 75.940 MHz 75.960 MHz 75.980 MHz Page 8 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. Frequency coordination and after-sale programming for different compatible frequency groups can be done through COMTEK’s Technical Support Services. GROUP 1 GROUP 2 GROUP 3 FREQUENCY FREQUENCY FREQUENCY 72.020 72.220 72.720 74.610 75.620 75.720 MHz MHz MHz MHz MHz MHz 72.080 72.180 72.720 74.770 75.580 75.920 MHz MHz MHz MHz MHz MHz 72.260 72.580 72.790 74.250 75.840 75.960 MHz MHz MHz MHz MHz MHz Multiple Channel Operation When multiple transmitters (more than two) are used in the same proximity, intermodulation interference often occurs. This condition is common to all radio receivers to some extent when multiple transmitters are used in the same operating area. The RF signals will “MIX” together generating additional signals. If these product frequencies are too close to a frequency to which the receiver can also respond, you will experience intermodulation interference which may cause undesirable operation. To avoid this type of self-interference when multiple transmitters are used in the same proximity, transmitting frequencies must be coordinated by selecting from frequencies in the same group. Page 9 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 Base station transmitter Page 10 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. RMK 75 Single rack-mount face plate Page 11 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 2.1mm DC power jack • BNC type RF output Audio Gain Control: Limited to 20 dB Frequency Modulation: 10 kHz deviation Operation Indicators: • LED bargraph VU meter • LED antenna load and coaxial cable condition indicator • LED DC power indicator RF Output Power: Maximum power output for FCC Part 90 (120mV) Antenna: • 19” Telescopic antenna mounts directly into top of transmitter • BNC RF output connector for optional external antenna Frequency Stability: Better than 0.002% digitally synthesized, crystal controlled Operating Frequency: 72.020 to 75.980 MHz (98 channels) FCC Compliance: Type Accepted under FCC Part 90 Harmonic and Spurious Emissions: Better than 50 dB below carrier Power Requirements: 12 Volts DC, 200 mA max Dimensions: 3 3/4" X 1 5/8" X 5 1/4" deep Frequency Response: 80 Hz to 10 kHz Weight: Audio Distortion: Less than 0.5% at 80% modulation 15 1/4 oz. NOTE: Specifications subject to change without notice Page 12 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. 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 FOR A PARTICULAR PURPOSE OF SUCH EQUIPMENT INCLUDING, WITHOUT LIMITATION, ANY WARRANTY THAT THE USE OF SUCH EQUIPMENT FOR ANY PURPOSE WILL COMPLY WITH APPLICABLE LAWS AND REGULATIONS. Service Policies Warranty repairs must be done by COMTEK. Only factory technicians are authorized to perform warranty service on the BST-75 transmitter. Before returning the BST-75 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 Web: www.comtek.com E-mail: sales@comtek.com 357 West 2700 South • Salt Lake City, Utah 84115 • Phone: (800) 496-3463 • Fax: (801) 484-6906 • www.comtek.com
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