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FMT- 25 VHF FM TRANSLATOR 862-09725

Issue 1A:

FMT-25

VHF FM TRANSLATOR

TECHNICAL MANUAL

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Summary of Contents for FMT-24

Page 1: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL ...

Page 2: ...09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL CONTENTS 1 Introduction 2 General Description 3 Technical Specifications 4 Operating Information 5 Installation Information 6 Technical Information 7 Maintenance information ...

Page 3: ...TRODUCTION This Manual contains the Operating technical and installation information for the FMT 25 VHF FM Translator The FMT 25 forms part of a new range of Professional VHF FM Re broadcasting equipment produced by Broadcast Solutions Electronics ...

Page 4: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL General Description ...

Page 5: ...solution for VHF FM Re broadcasting and only requires 1U rack space The unit includes a fully synthesized FM Receiver with Front end tracking filters and a highly selective Ceramic IF Filter A Tracking demodulator and 100kHz Low pass filter are also standard features of the receiver section The unit also includes a fully synthesized FM Modulator with provision for internal and external Baseband in...

Page 6: ...eters 6 Tx Power adjustment potentiometer 7 PSU Rx indicators and alarms 8 Power on off switch Switches a c Mains and dc 24V supplies 9 A C Mains input Europlug IEC connector for a c supply 10 Ext 24V dc input Positive and negative dc binding terminals 11 A C Mains Fuse Fuse 1Amp 230V or 2A 115V 12 Ground M5 Screw for chassis ground 13 Telemetry D15 female connector for remote commands and alarms ...

Page 7: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A Figure 1 Front and Rear panel layout ...

Page 8: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A Figure 2 Schematic Diagram of FMT 25 ...

Page 9: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL Technical Specifications ...

Page 10: ...000uV 75dB Rx Static selectivity RF Filter IF Filter and Rx baseband filter Frequency offset Selectivity 100kHz 0dB 200kHz 65dB 300kHz 90dB 400kHz 100dB 500kHz 110dB Rx Dynamic selectivity 75kHz deviation reference and 75uS de emphasis for 54dB S N ratio Stereo Frequency offset Selectivity 0kHz 46dB 100kHz 30dB 200kHz 6dB 300kHz 27dB 400kHz 35dB Rx baseband amplitude response Frequency Response 30...

Page 11: ...reo demodulator and decoder Frequency Distortion Separation Crosstalk 30Hz 0 15 50dB 50dB 1kHz 0 15 50dB 50dB 5kHz 0 25 50dB 50dB 15kHz 0 25 50dB 50dB General Tx Rx specifications Tx Rx Frequency range 87 5MHz to 108MHz Tx Rx Frequency separation 400kHz Tx Rx Frequency increments 50kHz steps synthesized Tx Rx Frequency stability 2ppm Tx RF Output power 25W Adjustable via front panel Tx Harmonics a...

Page 12: ...nput IEC Europlug A C Fuse 1A 230V 2A 115V 20mm Type Chassis Ground 5mm screw Fixing Front panel controls and indicators Control indicator Function RF Enabled led green Indicates Remote enable function Tx PLL Lock led green Indicates Tx PLL is in Lock RF Fault led red Indicates Forward power is low VSWR Fault led red Indicates Reflected power is high Temp Fault led red Indicates RF PA Temp is high...

Page 13: ...n fault Pins 5 and 6 RF PA VSWR Fault Voltage free contact s c when fault Pins 7 and 8 Low RF power Fault Voltage free contact s c when fault Pins 9 and 10 PSU Fault Voltage free contact s c when fault Pin 11 Tx Enable S c to Ground to disable Pin 12 Jig supply 22V at 20mA Pin 13 Stereo indicator npn open collector ground for stereo Pin14 PLL Lock indicator npn open collector ground for lock Pin 1...

Page 14: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL Operating Information ...

Page 15: ...larms 8 Power on off switch Switches a c Mains and dc 24V supplies 9 A C Mains input Europlug IEC connector for a c supply 10 Ext 24V dc input Positive and negative dc binding terminals 11 A C Mains Fuse Fuse 1Amp 230V or 2A 115V 12 Ground M5 Screw for chassis ground 13 Telemetry D15 female connector for remote commands and alarms 14 RF Output N Type 50 ohm female 15 Tx Auxiliary baseband input BN...

Page 16: ...ibed a c operation 7 b A C Fuse Accepts 1 Amp 20mm type fuse 9 c DC Input Red Black terminal posts for 24V Battery operation 8 d Ground post 5mm screw for grounding purposes e Telemetry 15 pin D type female for remote control monitoring 11 f De emphasis Switch to enable stereo decoder de emphasis 10 g Diversity input BNC input for Wideband MPX reserve 12 h Baseband outputs BNC outputs for re broad...

Page 17: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL Installation Information ...

Page 18: ...on off switch on the front panel is switched off before proceeding a A C MAINS SUPPLY 115V 50Hz Connect a c power cable to IEC connector on back panel b DC SUPPLY 24V dc Connect dc power input to the dc supply terminals on the back panel observing correct polarity c RF OUTPUT Connect the Antenna cable to the RF Output on the back panel using an N type connector or via suitable adapters d RF INPUT ...

Page 19: ... PWR ADJ potentiometer clockwise to set the RF output power to 25W This should be achieved with 16 Leds on Now check the PA CURRENT and REFL POWER readings PA CURRENT should be approximately 1 9 Amps REFL POWER should be less than 2 5W 16 Leds Check all the fault Leds on the front panel and ensure that there are no red Leds on The unit is now operational and only the final temperature must be moni...

Page 20: ...SLATOR 862 09725 Issue 1A The external cables and connectors are not normally supplied as standard kit and due to the various customer configurations the cable and connector requirements must be requested by the customer ...

Page 21: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL Technical Information ...

Page 22: ...state output and is applied to a Loop integrator IC3 and Loop filter IC14 whose dc output in turn controls the frequency of the Local oscillator via Varactor diode D7 Control sensitivity is approximately 2MHz Volt The Local oscillator output can be monitored via SK2 Front End Filters and Amplifier The Front End Filter is Self Tuning and is configured into two sections pre and post amplifier The RF...

Page 23: ... of the demodulator at pins 8 and 9 contain the recovered baseband and also a differential dc offset proportional to the 10 7MHz RF input frequency offset This dc offset is applied to IC11 B which amplifies the dc offset and applies it to Varactor diodes D8 and D9 which in turn tune the demodulator This corrects the error and ensures the distortion is minimized C90 and C96 are provided to initiall...

Page 24: ...08MHz The synthesizer consists of a single modulus loop with a divide by 64 pre scaler IC6 A 12 8MHz TCXO IC7 provides an accurate and stable reference for the synthesizer The reference is then divided by two by IC30 Ato 6 4MHz This reference is applied direct to the fixed divider in the synthesizer IC18 This divides by 8192 to obtain a comparison frequency of 781 25Hz This mode of operation provi...

Page 25: ...or a High Reflected RF Fault set by R215 REFL Alarm cal The output is then routed to TR14 and RL2 C to provide contacts for Telemetry and Alarm indications The output from IC25 B is also routed to comparator IC26 C that sets the Reflected Trip level via R211 REFL Alarm trip When activated the output is routed to IC26 D which performs the function of the timer The timer allows the Reflected power r...

Page 26: ... 2 Reflected power R3 Position 3 Baseband level R4 Position 4 The Field Forward and Reflected signals are dc voltages whilst the Baseband signal is a dynamic a c signal These inputs are on SK1 The signals are routed via IC2 to a full wave peak detection circuit IC3 C and IC3 D which has a fast attack time and slow decay time to enable visual operation of the dynamic signal This output is routed to...

Page 27: ... SK1 pin1 and 2 and 12V SK1 pin 23 IC6 regulates the 12V supply and IC7 regulates the 5V supply v FMT POWER SUPPLY PCB 980808 A C Input supply The a c input to the power supply module is provided by an external 24V a c winding on the A C Mains transformer The winding is connected to SK1 pin 1 and pin 3 A Full wave Bridge rectifier D1 is used to rectify the a c input with capacitors C1 to C9 provid...

Page 28: ... output to input of the Final RF stage TR2 Class C Push pull Mosfet The gate bias voltage for this device is provided via PL1 R14 and R14 is adjusted to limit the maximum output power of the device The output of TR2 is routed to Wideband Transformer T2 which converts the balanced output of TR2 to unbalanced The output from T2 is routed to the RF Low pass filter The RF filter consists of a seventh ...

Page 29: ...FMT 25 VHF FM TRANSLATOR 862 09725 Issue 1A FMT 25 VHF FM TRANSLATOR TECHNICAL MANUAL Maintenance Information ...

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