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
Issue 1A:
FMT-25
VHF FM TRANSLATOR
TECHNICAL MANUAL
General Description

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