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SRK Electronics MFTX100 Operation And Service Manual

100w mf am transmitter
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SRK Electronics
MFTX100
100W MF AM transmitter
Operation and service manual
Manual version 1.0
Issued 17 July 2013
This manual covers all units from serial number 388

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Summary of Contents for SRK Electronics MFTX100

  • Page 1 SRK Electronics MFTX100 100W MF AM transmitter Operation and service manual Manual version 1.0 Issued 17 July 2013 This manual covers all units from serial number 388...

  • Page 2: Table Of Contents

    MFTX100 Contents OVERVIEW SPECIFICATIONS WARRANTY UNPACKING INSTALLATION 5.1. General 5.2. Environmental 5.3. Electrical supply 5.4. Earthing 5.5. Antenna 5.6. Audio feed EXTERNAL VIEWS 6.1. Front panel 6.1.1. (1) Display 6.1.2. (2) Control knob 6.1.3. (3) RF sample connector 6.1.4. (4) Air vents 6.2.
  • Page 3 MFTX100 7.6.1. Reading elapsed days 7.6.2. Setting date and time 7.7. Night power menu 7.7.1. Enabling and disabling night-time power switching 7.7.2. Setting night-time power start and stop times 7.7.3. Setting night-time power REMOTE CONTROL 8.1. Analogue remote control 8.1.1.
  • Page 4 MFTX100 14.8. PWM/RF board schematic 14.9. Output board schematic 14.10. Main board, PCB overlay 14.11. Remote control board, PCB overlay 14.12. PWM/RF board PCB overlay 14.13. Output board PCB overlay CHANGE HISTORY SRK Electronics...

  • Page 5: Overview

    MFTX100 1. Overview The MFTX100 is a 100W AM transmitter designed for continuous unattended operation. Amongst others, the MFTX100 has the following features: • 1-100W carrier rest power • Power efficient design • Pseudo frequency agile • Electronically balanced professional audio input •...

  • Page 6: Specifications

    MFTX100 2. Specifications RF output power (0% mod) 1-100W, settable in 1W steps RF output power (peak) 500W RF output connector N female Harmonics and spurious >-65dBc Factory set frequency range 531-1701KHz User set frequency range within 90KHz of factory setting...

  • Page 7: Warranty

    MFTX100 3. Warranty SRK warrants that the equipment is newly manufactured and is free of any defects in materials and workmanship. SRK shall rectify any defect in the equipment which is notified in writing to SRK by the Customer within the period of 3 years after the date of acceptance where such defect renders the equipment unable to conform with the specifications and configuration prescribed in this manual.

  • Page 8: Unpacking

    MFTX100 4. Unpacking This section details the way in which the MFTX100 should be unpacked upon receipt by the customer. Upon receipt the transmitter should be visually inspected to ensure that no damage has occurred in transit. The packing should be stored and used should it be necessary to return the transmitter to the manufacturer.

  • Page 9: Installation

    MFTX100. Departure from the instructions contained herein may void any warranty provided by SRK. The MFTX100 has been designed to be mounted in a standard 19” rack frame, where it will occupy 3 rack units. However, the transmitter may also be used in a free standing situation, so long as all other requirements are met as below.

  • Page 10: Earthing

    MFTX100 5.4. Earthing Adequate earthing of the transmitter is vital to ensure long term reliability and user safety. The electrical supply must be earthed, via the earthing pin of the IEC connector. In countries where power outlet earthing is merely optional, an earthed outlet must be used.

  • Page 11: External Views

    MFTX100 6. External views 6.1. Front panel 6.1.1. (1) Display This is a backlit 2 line x 40 character display where all parameters are shown. Used in conjunction with the control knob, parameters can be read and changed by the user.

  • Page 12: 4) Air Vents

    MFTX100 6.1.4. (4) Air vents These vents allow convection cooling of the transmitter and must not be obstructed. 6.2. Rear panel 6.2.1. (1) Audio input connector Balanced audio input. XLR (Cannon) 3 pin socket. Pin 1 is ground, pin 2 is +ve and pin 3 is –ve.

  • Page 13: 4) Earth Stud

    MFTX100 6.2.4. (4) Earth stud M6 earth stud for connection to the antenna system earth. This must be connected to a reliable earth for the best possible lightning protection. 6.2.5. (5) Air vent Allows free air convection cooling of the transmitter, along with the vents on the front panel.

  • Page 14: Front Panel Operation

    MFTX100 7. Front panel operation All parameters and functions of the transmitter may be accessed via the front panel using the display and control knob. The knob is a multipurpose control that can be rotated clockwise or anticlockwise or pushed like a button, depending on the desired action.

  • Page 15: Rf Menu

    MFTX100 active then FAIL is shown. See section xxx for more details about individual alarms. The summary screen is shown when the transmitter is first switched on. No parameters can be changed whilst displaying the summary screen. 7.2. RF menu...

  • Page 16: Setting Carrier Power

    MFTX100 7.2.1. Setting carrier power As alluded to above, to set the carrier power, rotate the control knob until the flashing arrow is adjacent to and pointing towards “Set Pwr=”. Momentarily pressing the knob will cause the set power to flash. Whilst flashing, rotating the knob in the clockwise direction will increase the power, up to 100 watts.

  • Page 17: Reading Forward And Reflected Power

    Note that due to the advanced design of the MFTX100, it is not necessary to change audio gain when changing set power. The ratio of carrier power to audio level is entirely determined by the gain setting.

  • Page 18: Enabling And Disabling The Audio Low Pass Filter (Lpf)

    MFTX100 7.3.3. Enabling and disabling the audio low pass filter (LPF) The status of the audio low pass filter (9KHz Bessel response) is shown next to “LPF=”. This is permanently on. 7.3.4. Enabling and disabling audio compressor The status of the audio compressor is shown next to “Compressor =”. This is permanently off.

  • Page 19: Date/Time Menu

    MFTX100 “SWR=” shows the status of the SWR alarm. If the reflected power is greater than 10W then the SWR alarm will be activated and “FAIL” will appear in this field. “INT’LK=” shows the status of the interlock signal of the analogue remote control port.

  • Page 20: Setting Date And Time

    7.7. Night power menu The output power of the MFTX100 may be automatically reduced during the hours of darkness to allow for the disappearance of the D layer. This can be done by enabling the night-time power between a given start and stop time.

  • Page 21: Setting Night-Time Power

    MFTX100 7.7.3. Setting night-time power Once the knob is pressed to set the “to” seconds the night power will flash. This can be set by rotating the knob to show the desired carrier rest power, analogous to the set power during normal operation. If the knob is pressed one last time all values will be stored in memory and if the current time falls between the from and to times, the output power will immediately be set to the night-time power.

  • Page 22: Remote Control

    MFTX100 8. Remote control The MFTX100 has two means of remote control and monitoring. The analogue remote control is a very basic analogue interface which allows the transmitter to be turned on/off and audio and other alarms to be monitored. The serial remote control is a sophisticated RS232 based interface that allows all parameters and controls to be accessed.

  • Page 23: Audio Ok Relay

    MFTX100 8.1.3. Audio OK relay If the modulation depth falls to 2% or below continuously for more than 30 seconds the AUDIO OK relay contact will open and stay open until the modulation depth rises above 2%, even instantaneously. The differential voltage on this contact should be limited to 120VAC or 24VDC and the current should be less than 0.5A AC or DC.

  • Page 24: Alarms

    9.1. SWR alarm If the reflected power exceeds 10W then the MFTX100 will automatically reduce the forward power to make the reflected power equal to 10W. This is the result of the operation of a dynamic control loop that follows the peaks of modulation and will act within a few milliseconds of detecting a reflected power of greater than 10W.

  • Page 25: Pll Alarm

    MFTX100 is active (unless the transmitter has experienced a catastrophic failure) but the modulation may well be heavily distorted. Operation of this alarm indicates an internal failure of the transmitter that requires repair by a qualified technician. 9.4. PLL alarm The PLL alarm becomes active if the transmitter is unable to generate the correct frequency.

  • Page 26: Maintenance

    MFTX100 10. Maintenance The MFTX100 requires little routine maintenance. The heatsink and ventilation grills should be regularly inspected and cleaned if necessary. It is also good practice to log all parameters on a monthly basis to allow changes in operating conditions to be identified.

  • Page 27: Circuit Description

    MFTX100 11. Circuit description 11.1. Theory of operation 11.2. Transmitter overview 11.3. Main board 11.4. Remote control board 11.5. PWM/RF board 11.6. Output board SRK Electronics...

  • Page 28: Abbreviations

    MFTX100 12. Abbreviations Amp(s) Alternating Current Amplitude Modulation Antenna Tuning Unit Bill Of Materials (parts list) Centigrade Decibels Decibels relative to carrier level Decibels relative to 1mW (into 50 or 600 ) Hertz DC current Kilo, kilo-ohm Kilogram Kilohertz Low Pass Filter...

  • Page 29: Bill Of Materials

    MFTX100 13. Bill of materials 13.1. Top level BOM SRK Electronics...

  • Page 30: Main Board

    MFTX100 13.2. Main board SRK Electronics...

  • Page 31: Remote Control Board

    MFTX100 13.3. Remote control board SRK Electronics...

  • Page 32: Pwm/Rf Board

    MFTX100 13.4. PWM/RF board SRK Electronics...

  • Page 33: Output Board

    MFTX100 13.5. Output board SRK Electronics...

  • Page 34: Drawings

    MFTX100 14. Drawings 14.1. Overall Schematic SRK Electronics...
  • Page 35 MFTX100 SRK Electronics...

  • Page 36: Main Board, Top Level Schematic

    MFTX100 14.2. Main Board, top level schematic SRK Electronics...
  • Page 37 MFTX100 SRK Electronics...

  • Page 38: Main Board, Audio Schematic

    MFTX100 14.3. Main board, audio schematic SRK Electronics...
  • Page 39 MFTX100 SRK Electronics...

  • Page 40: Main Board, Control Schematic

    MFTX100 14.4. Main board, control schematic SRK Electronics...

  • Page 41: Main Board, Pll Schematic

    MFTX100 14.5. Main board, PLL schematic SRK Electronics...

  • Page 42: Main Board, Digital Schematic

    MFTX100 14.6. Main Board, Digital schematic SRK Electronics...

  • Page 43: Remote Control Board Schematic

    MFTX100 14.7. Remote control board schematic SRK Electronics...

  • Page 44: Pwm/Rf Board Schematic

    MFTX100 14.8. PWM/RF board schematic SRK Electronics...

  • Page 45: Output Board Schematic

    MFTX100 14.9. Output board schematic SRK Electronics...

  • Page 46: Main Board, Pcb Overlay

    MFTX100 14.10. Main board, PCB overlay SRK Electronics...

  • Page 47: Remote Control Board, Pcb Overlay

    MFTX100 14.11. Remote control board, PCB overlay SRK Electronics...

  • Page 48: Pwm/Rf Board Pcb Overlay

    MFTX100 14.12. PWM/RF board PCB overlay SRK Electronics...

  • Page 49: Output Board Pcb Overlay

    MFTX100 14.13. Output board PCB overlay SRK Electronics...

  • Page 50: Change History

    MFTX100 15. Change history Version No. Release Date Description of change(s) 21/7/13 First issue 21/10/13 SRK Electronics...

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