Crown Low Power Transmitters - Crown Broadcast

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questo mondo, forse, uno si dice diciamo che in se ma in scrivendo con questo mondo, forse, uno si dice diciamo che se ma ma in scrivendo con scrivendo con questo mondo, forse, uno si dice che diciamo se ma scrivendo con ma in scrivendo con questo mondo, forse, uno si dice scrivendo con che diciamo che diciamo se ma se ma scrivendo con 4.13 Chassis The AC power supply components, as well as the bridge rectifier and main filter capacitor are mounted on the chassis. Switching in the power-entry module configures the power transformer for 100, 120, 220, or 240 VAC; see section 2.2 for switching and fuse information. A terminal strip with MOV voltage-surge suppressors and in-rush current limiters is mounted on the chassis between the power entry module and the toroidal power transformer. WARNING Shock hazard! Do not attempt to short the capacitor terminals. A bleeder resistor will discharge the capacitor in approximately one minute after shutdown. The main energy-storage/filter capacitor, C1001, is located between the voltage and power regulator boards. The DC voltage across the capacitor will be 45–55 volts (FM30 and FM100) or 65–70 volts (FM250) when the carrier is on. 4.14 RF Output Filter & Reflectometer The RF low-pass filter/reflectometer are located in the right-hand compartment on the top of the chassis. See Illustration 6–14 and accompanying schematic for more information. A ninth-order, elliptic, low-pass filter attenuates harmonics generated in the power amplifier. The capacitors for the filter are circuit board pads. The reflectometer uses printed circuit board traces for micro-strip transmission lines. Transmission line segments (with an impedance of about 82 ohms) on either side of a 50–ohm conductor provide sample voltages representative of the square root of forward and reverse power. DC voltages, representative of forward and reflected power, go through a bulkhead filter board to the motherboard, then to the metering board, where they are processed for power control and metering and for SWR metering and protection. 4–14 FM30/FM100/FM250 User's Manual
4.15 Receiver Circuit Board Option This option allows the transmitter to be used as a translator. The receiver board receives terrestrially fed RF signal and converts it to composite audio which is then fed into the exciter board. Microprocessor controlled phase lock loop technology ensures the received frequency will not drift, and multiple IF stages ensure high adjacent channel rejection. Refer to illustrations 4–6, 6–16 and its schematic for the following discussion. The square shaped metal can located on the left side of the receiver board is the tuner module. The incoming RF signal enters through the BNC connector (top left corner) and is tuned through the tuner module. Input attenuation is possible with jumper J1 on the top left corner of the receiver board. Very strong signals can be attenuated 20 dB automatically by placing the jumper on the left two pins (“LO” position). An additional 20 dB attenuation is also available with the jumpers in the top left corner of the board. The frequencies are tuned by setting switches SW1 and SW2 (upper right corner). These two switches are read upon power up by the microprocessor (U4). The microprocessor then tunes the synthesizer IC MC145170 (U3) to the selected frequency. The switches frequency range is 87.9 Mhz at setting “00” to 107.9 Mhz at setting “64”. Other custom ranges are available. The synthesizer chip works on a phase lock loop system. It receives the frequency information from pin 6 of the tuner module, then goes through a FET buffer amplifier (Q2) on its way to synthesizer IC (U3). The synthesizer feeds back a DC voltage through two resistors to pin 4 of the tuner module. Different frequencies cause different tuning voltages to go to the tuner module to tune it on frequency. The frequency synthesizer locks on to the exact frequency needed and adjusts the DC voltage accordingly. The microprocessor tunes the frequencies of the synthesizer IC, but the DC tuning voltage is somewhat dependent on the tuner module. Generally, the voltage is around 0.5 volt DC for tuning 88.1 MHz, and from 5.5 to 6.5 volts DC for tuning 107.9 MHz. The 10.7 MHz IF frequency comes out of the tuner module on pin 5 and is coupled into the first filter FL1; passes through FL1 RF In Receiver Module ® FM250 Illustration 4–6 Receiver Board Principles of Operation 4–15
Page 1 and 2:
® FM30/FM100/FM250 Broadcast Trans
Page 3 and 4: Contents Section 1—Getting Acquai
Page 5 and 6: Section 5—Adjustments and Tests .
Page 7 and 8: I INFORMATION Section 1—Getting A
Page 9 and 10: 1.2 Applications and Options Crown
Page 11 and 12: 1.2.5 Translator A receiver configu
Page 13 and 14: 1.3 Transmitter/Exciter Specificati
Page 15 and 16: Note: We set voltage and ampere req
Page 17 and 18: ® Section 2—Installation This se
Page 19 and 20: 120Vac Illustration 2-1 Removing th
Page 21 and 22: 2.2.3 Battery Power Your transmitte
Page 23 and 24: 2.3.1 Modulation Compensator The Mo
Page 25 and 26: Frequency SW1 SW2 87.9 0 0 88.0 8 0
Page 27 and 28: 2.6 Audio Input Connections Attach
Page 29 and 30: SCA IN COMPOSITE IN MONITOR RIGHT L
Page 31 and 32: Pin Number Function 1 Ground 2 (no
Page 33 and 34: Section 3—Operation This section
Page 35 and 36: 3. Verify the following: a. The bot
Page 37 and 38: 3.3 Front Panel Bar-Dot Displays Ba
Page 39 and 40: 3.7 RF Output Control Set this cont
Page 41 and 42: in questo mondo, erono due forse, u
Page 43 and 44: 4.2 Audio Processor Circuit Board T
Page 45 and 46: Stereo Generator Board ® FM250 Ill
Page 47 and 48: Principles of Operation 4-7
Page 49 and 50: To get a direct reading of SWR, the
Page 51 and 52: 4.8 Voltage Regulator Circuit Board
Page 53: 4.11 RF Driver (FM100/FM250) The RF
Page 57 and 58: Section 5—Adjustments and Tests T
Page 59 and 60: Using a Modulation Monitor 1. Set t
Page 61 and 62: 5.3.4 FSK Balance Control An FSK si
Page 63 and 64: 5.8 Bias Set (RF Power Amplifier) T
Page 65 and 66: 5.14 Audio Frequency Response For t
Page 67 and 68: Section 6—Reference Drawings The
Page 70 and 71: 6.2 Board Layouts and Schematics Il
Page 72 and 73: Illustration 6-6 Stereo Generator B
Page 74 and 75: SEE NOTE 10 TOP SIDE COMPONENT MAP,
Page 76 and 77: D 8169-1 Illustration 6-8 RF Meteri
Page 79 and 80: 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
Page 81 and 82: R27 D 8167-5 Illustration 6-10 Disp
Page 84: 2 4 6 8 3 2 1 1 3 5 7 9 6 5 4 3 2 1
Page 87 and 88: R20 R19 Illustration 6-13 Power Amp
Page 89 and 90: Illustration 6-14 RF Output Filter
Page 92 and 93: F 1 2 3 4 5 6 7 8 ADDED TO PWB (200
Page 96 and 97: Section 7—Service and Support We
Page 98 and 99: Crown Broadcast Three Year Limited
Page 100 and 101: Factory Service Instructions To obt
Page 102 and 103: Transmitter efficiency output RF Po
Page 104 and 105:
A B C AF ALC AM bandwidth BCD BFO B
Page 106 and 107:
A B C pre-emphasis processing recei
Page 108 and 109:
Symbols 19-kHz level adjustment 5-4
Page 110 and 111:
L labels 1-10 LEDs 3-5, 4-10 line v
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Crown Low Power Transmitters - Crown Broadcast

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