Larcon FMT-24 User manual

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

FMT-25 VHF FM TRANSLATOR 862-09725
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

FMT-25 VHF FM TRANSLATOR 862-09725
Issue 1A:
INTRODUCTION
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.

FMT-25 VHF FM TRANSLATOR 862-09725
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FMT-25
VHF FM TRANSLATOR
TECHNICAL MANUAL
General Description

FMT-25 VHF FM TRANSLATOR 862-09725
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GENERAL DESCRIPTION
The FMT-25 VHF FM Translatoris a compact unit requiring only 1U Rack space. The
unit is designed for use in VHF FM Stereo Broadcasting in the 87.5MHz to 108MHz,
band. The unit will perform the function of a “Relay receiver” and “25W FM
Exciter”, providing Local (Display) and Remote (Telemetry) functions.
TheFMT-25 offers standard featuresthat include:
•Automatic tuning of Rx Front-end filters.
•Fully synthesized in 50kHz steps (Tx and Rx).
•Rx Diversity operation capability.
•A/C and DC (+24V) operation.
•ALC for RF Power control.
•Telemetry output.
•Rx Headphone output.
•RF Monitor output.
•Comprehensive metering and indicators.
The FMT-25 offers a range of customer options that include:
•ID Module for internal SCA insertion.
The FMT-25 provides a High quality, compact and versatile 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 ahighly selectiveCeramic IF Filter. A Tracking demodulator and 100kHz Low
pass filter are also standard features of the receiver section. The unit also includes a
fully synthesizedFM Modulator with provision for internal and external Baseband
inputs. The FMT-25 has a 25-Watt RF Power amplifier module with integral SMPSU.
Low pass RF Filter and couplers are standard on this module.
The FMT-25 is equipped with a +24V dc input, which can be used for Battery/Solar-
powered operation or as back up for mains failure condition. The dc input is internally
fused for protection purposes. The rectified a/c input is also fused internally, while the
a/c mains input is fused on the rear panel.
The schematic diagram of the FMT-25 is shown in figure 2 below.
3. STRUCTURE.
The FMT-25 comprises of the following modules.
a) Display PCB (378-Z0028).
b) Main PCB (378-Z0027).
c) RF PA Module (980801).

FMT-25 VHF FM TRANSLATOR 862-09725
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d) PSU Module (980808).
Each module is Field replaceable, in line with BSE’s maintenance philosophy. This
allows the customer to change a module, or to upgrade options easily.
4. FUNCTIONAL DESCRIPTION.
Refer to the Front and Rear panel layout in figure 1.
1) RF monitor (BNC 50 ohms female).
2) Rx Headphone monitor (Stereo ¼ inch Jack socket).
3) Tx indicators and alarms.
4) Bargraph meter (20 dot).
5) Bargraph meter function selector (Selects one of four metered parameters).
6) Tx Power adjustment (potentiometer).
7) PSU / Rx indicators and alarms.
8) Powe r on/off switch: Switches a/c (Mains) and dc (+24V) supplies.
9) A/C Mains inputEuroplug (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 (BNC female for SCA/SST Sub-carrier injection).
16) Tx Baseband input(BNC female for composite/MPX injection).
17) Rx Baseband output(BNC female for Rx composite/MPX output).
18) Input Receiver (BNC 50 ohms female for received RF input).

FMT-25 VHF FM TRANSLATOR 862-09725
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Figure 1: Front and Rear panel layout.

FMT-25 VHF FM TRANSLATOR 862-09725
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Figure 2: Schematic Diagram of FMT-25

FMT-25 VHF FM TRANSLATOR 862-09725
Issue 1A:
FMT-25
VHF FM TRANSLATOR
TECHNICAL MANUAL
Technical Specifications

FMT-25 VHF FM TRANSLATOR 862-09725
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FMT-25 SPECIFICATIONS
Electrical characteristics
Typical Rx Sensitivity: 75kHz-deviation reference with 75uS de-emphasis (Stereo)
RF Input level Stereo S/N ratio
20uV 50dB
50uV 56dB
100uV 60dB
500uV 70dB
1000uV 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
30Hz to 53kHz ±0.1dB
53kHz to 95kHz ±1dB
≥200kHz ≤-65dB

FMT-25 VHF FM TRANSLATOR 862-09725
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Rx baseband performance: Stereo with 75kHz deviation and de-emphasis off.
Tested at 1mV, RF input.
Frequency Distortion Separation Crosstalk
30Hz ≤0.25% ≥50dB ≥50dB
1kHz ≤0.25% ≥50dB ≥50dB
5kHz ≤0.25% ≥50dB ≥50dB
15kHz ≤0.25% ≥50dB ≥45dB
Tx baseband amplitude response: Input via Tx baseband input.
Frequency Response
1Hz -3dB
30Hz to 53kHz ±0.1dB
53kHz to 100kHz ±0.25dB
Tx baseband performance: Stereo with 75kHz deviation.
Tested with FM Stereo 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 and spurious ≤-60dBc
Tx out of lock attenuation ≥70dB
Tx AM Non synchronous ≤-60dBc
Tx baseband i/p Z 10k ohms
Tx baseband i/p sensitivity 3.5V p-p for 75kHz peak deviation
Tx Aux. baseband i/p Z 10k ohms
Tx Aux. baseband i/p sensitivity 3.5V p-p for 3kHz peak deviation

FMT-25 VHF FM TRANSLATOR 862-09725
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Environmental Specifications
A/C Input power 115V ±10% (230V Optional)
A/C Frequency variation 50Hz to 60Hz
DC Input power +24V Battery (+24V to +28V)
Power consumption Approximately 70W
Storage temperature -40°C to +60°C
Operating temperature -10°C to +45°C
Relative Humidity 20% to 90% non condensing
Operating Altitude ≤2500m above sea level
Cooling system Convection (Blower option)
Dimensions 480mm x 450mm x 44.4mm
Physical mass Approximately 7kg
Back Panel connectors and Functions.
Function Connector
RF output N Type Female (50 ohm)
Rx input BNC Female (50 ohms)
Rx baseband o/p BNC Female
Tx baseband i/p BNC Female
Tx Aux. baseband i/p BNC Female
Telemetry (input/output) D15 Female
Ext. dc Input (+24V Battery) 2 x Terminal posts
A/C Mains input 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
TL ID led (yellow) Indicates TL ID Module installed
A/C Supply led (green) Indicates A/C Supply is present
EXT DC led (green) Indicates +24V DC Supply is present
Rx PLL Lock led (green) Indicates Rx PLL is in Lock
Mute led (red) Indicates Rx is Muted
Program loss led (red) Indicates Loss of program
PSU Fault led (red) Indicates PSU Failure
Function select LED’s (yellow) Indicates meter function selected
Tx Power adjust potentiometer Sets required Tx RF Power
Headphone stereo monitor jack 600 ohm headphones for Rx program
RF Monitor BNC (50 ohm) Samples Tx output for test purposes

FMT-25 VHF FM TRANSLATOR 862-09725
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Telemetry controls and alarms (via 15-pin D type female connector).
Pin number on SK17 Description
Pin 1 OV
Ground
Pin 2 Rx Mute
(Contact s/c to ground when muted)
Pins 3 and 4 RF PA Temperature Fault
(Voltage free contact, s/c when 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 15 14 sec. Program loss indicator
npn open collector / ground for program

FMT-25 VHF FM TRANSLATOR 862-09725
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FMT-25
VHF FM TRANSLATOR
TECHNICAL MANUAL
Operating Information

FMT-25 VHF FM TRANSLATOR 862-09725
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OPERATING INFORMATION
Translator Applications:
•Stand alone Translator: When used with VHF receive and Transmit antennas.
•High power Translator: When used with VHF receive and Transmit antennas and
Wideband VHF RF Amplifier.
•Translator with Space Diversity: When used with VHF receive and Transmit antennas
with a Reserve Receiver connected in Diversity mode.
Operating and interface information.
Refer to the Front and Rear panel layout in figure 1.
1) RF monitor (BNC 50 ohms female).
2) Rx Headphone monitor (Stereo ¼ inch Jack socket).
3) Tx indicators and alarms.
4) Bargraph meter (20 dot).
5) Bargraph meter function selector (Selects one of four metered parameters).
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.
14) RF Output (N Type 50 ohm female).
15) Tx Auxiliary baseband input (BNC female for SCA/SST Sub-carrier injection).
16) Tx Baseband input (BNC female for composite/MPX injection).
17) Rx Baseband output (BNC female for Rx composite/MPX output).
18) Input Receiver (BNC 50 ohms female for received RF input).
Metered parameters
•Field strength: 3mV full scale (bottom scale).
•Forward RF Power level: 30W full scale (top scale).
•Reflected RF Power level: 3W full scale (top scale).
•Baseband level: 3V-rms full scale (top scale).
To adjust RF output power, select “Forward” on function select switch and adjust TX
PWR ADJ control to set desired RF output power.

FMT-25 VHF FM TRANSLATOR 862-09725
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Indicating LED’s:
•A/C Supply: Green led indicates A/C power is On.
•EXT DC: Green led indicates +24V ext. DC power is On.
•Rx PLL Lock: Green led indicates PLL lock is achieved.
•Mute:Red led indicates Rx is muted.
•Program Loss: Red led indicates loss of Rx program/modulation.
•PSU Fault: Red led indicates psu failure.
•RF Enabled: Green led indicates RF is enabled.
•Tx PLL Lock: Green led indicates PLL lock is achieved.
•RF Fault: Red led indicates low RF output.
•VSWR Fault: Red led indicates high-reflected power.
•Temp Fault: Red led indicates high temperature in RF PA module.
•TL ID: Yellow led indicates ID module is connected.
Rear panel
(a) A/C Input: IEC male connector for prescribed 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-broadcast purposes. (12)
(i) Remote PLL: 15 pin D type (female) to set remote frequency. (14)
(j) RF Input: N Type 50 ohm (female) for RF input. (15)
Frequency Selection
The operating frequency will normally be set at factory configuration, but if a different operating (
receive or transit) frequency is necessary then the unit top cover has to be removed and a new
frequency selected on the Translator main PCB (378-Z0027).This is done by setting the DIL
switches as detailed in Table 3 in the Installation Section of this manual.

FMT-25 VHF FM TRANSLATOR 862-09725
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FMT-25
VHF FM TRANSLATOR
TECHNICAL MANUAL
Installation Information

FMT-25 VHF FM TRANSLATOR 862-09725
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INSTALLATION
INSTALLATION
STAND ALONE CONFIGURATION (FM Translator)
The following information sets out the general requirements for installation and operation of
the above equipment in a "stand alone" configuration.
Note: The operating frequency will normally be set at factory configuration, but if a different
operating ( receive or transit) frequency is necessary then the unit top cover has to be
removed and a new frequency selected on the Translator main PCB (378-Z0027).This is done
by setting the DIL switches as detailed in Table 3.
1. ELECTRICAL CONNECTIONS
Ensure that the power 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.
Connect RF input to BNC input, Input Receiver, on the back panel.
Note: When the Telemetry connector is not in use the unit requires no external commands to
enable the RF.
2. OPERATION
With the electrical connections completed above the unit is now ready for operation.
a) SWITCH ON SEQUENCE
Adjust the RF power control on the front panel, fully acw. then set the power on/off
switch to ON.
b) FRONT PANEL LED's:
RF ENABLE (green led) ON

FMT-25 VHF FM TRANSLATOR 862-09725
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TX PLL LOCK (green led) ON
RF FAULT (red led) ON
VSWR FAULT (red led) OFF
TEMP FAULT (red led) OFF
TL ID (yellow Led) OFF
AC SUPPLY (green led) ON
EXT DC (green led) ON
RX PLL LOCK (green led) ON
MUTE (red led) OFF
PROGRAM LOSS (red led) OFF
PSU FAULT (red led) OFF
c) ALC METER (not fitted on this unit).
d) MULTIMETER
Select the four functions in turn and check the meter readings:
•FIELD Indication of received RF level.
•FORWARD POWER 0 Watts (no Leds on).
•REFLECTED POWER 0 Watts (no Leds on).
•BASEBAND Indication of received RF level.
e) SETTING THE RF POWER LEVEL
Select FWD POWER on the Multimeter and observe the reading.
Adjust the Front panel TX 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 monitored after
approximately 15 minutes. The temperature reading on the front panel Multimeter should
settle down to approximately 12°C above Room temperature.
MECHANICAL
The unit is designed to fit in a standard 19 inch rack, cabinet structure. There is a Slide rail kit
(option) available for this purpose which allows the unit to be installed in this manner.
Due to the weight of the unit it is not recommended to mount the unit without proper
support.
INTERCONNECTIONS

FMT-25 VHF FM TRANSLATOR 862-09725
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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.