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FM Transmitter 

Sistemas Electrónicos S.A                                                                                                                       EM 100 DIG

 Technical Manual - v1.2 -  November 2005

        18

Therefore, the audio level shall be constantly and correctly monitored and adjusted, to prevents as 
much as possible, the internal limiter from cutting in. On the other hand, the audio level should be as 

high as possible, to achieve the best signal/noise ratio on reception. 

The tendency to over-process audio signals is common in many local broadcasting stations:some 
sort of processing is advisable and we recommend using a top grade multiband compressor, but 

not  to  compress  the signal  too  much  as this impairs the original dynamics. 

The audio response of the EM-100 DIG transmitter is extremely flat, without perceivable loss on low 
and high audio frequency: for this reason large frequency alterations of the audio signal supplied by 
using a so-called “frequency equalizer,” are not advisable. An increase of the low and high 

frequency contents of the audio signal by more than a few dB can cause general degradation of 
modulation dynamics and improper functioning of the limiter. 

2.3.4  RS232 Serial Port. 

The RS-232 port manages only Tx, Rx and Return data signals, with no handshake. Being the two 
former signals wired inverted to the port, it need a simple straight wired serial cable with appropriate 

connectors:usually a female DB-9 or DB-25 female to the PC port and a male DB-9 connector at the 
transmitter end. Appropriate software is needed for communication. OMB can provide this software 
and also Telemetry Equipment at request. Do not connect the cable with neither transmitter or PC 
energized.

2.3.5  Parallel REMOTE Port. 

Remember that this port accommodates some lines for simple direct control / monitor on a DB-9 
male connector. They are: 

PIN

DESCRIPTION

1

GND

2

ON THE AIR      

A +12V/10k

:

 signals that the transmitter is delivering substantial RF power 

3

FORWARD POWER   

A signal proportional to transmitted power is present, with a pseudo square law. 
Range is 0-5V

DC

 /10K

:

 impedance.On EM-100 DIG,  5V stands for 100W. 

4 - 
5

GND

6

RF ENABLE   

A shorted circuit to ground disables RF. Signal level +10V

DC

/1mA max. 

7

FAIL URE            

Logic low signal means alarm. Correct functioning is signalled by +12V/10K

:

Maximum current sinking capability <10mA. 

8

GND

9 - 

Summary of Contents for EM 100 DIG

Page 1: ...OPE Factory Camino de los Albares 14 Tlf 976 50 35 80 Fax 976 50 38 55 50410 CUARTE DE HUERVA Zaragoza ESPAÑA Sales Dpt Avda San Antonio 41 Tlf 976 50 46 96 Fax 976 46 31 70 50410 CUARTE DE HUERVA Zaragoza ESPAÑA E mail europa omb com Web www omb es OMB USA 3100 NW 72nd Avenue Unit 112 MIAMI Florida 33122 Ph 305 477 0973 305 477 0974 Fax 305 477 0611 E mail usa omb com Web www omb com ...

Page 2: ... 40ºC for Sound Broadcast equipments 6 In case of operation at abnormally high or extremely high temperatures over 30 to 40 º C it is obligatory to install a forced cooling system that will keep temperature below its upper limit In case of operation at abnormally or extremely low temperatures it will be obligatory to install a thermostatic controlled heating system for equipment s room 7 Both equi...

Page 3: ...age of equipments within inadequate warehouses or outdoors once equipments are delivered to transportist agency About Projects________________________________________________________________ 1 O M B Sistemas Electronicos S A is not responsible of inadequate use of equipments made or registered by our Company accomplishing propagation projects that are not performed by our Specialists About Systems...

Page 4: ...ectrónicos S A of the Guarantee Activation Manual returned to OMB by Customer If such Document is not received this Warranty will be voided All repairings or adjustments covered by this Warranty are free of workmanship materials costs and expenses but postage and transportation expenses of equipments and O M B technical personnel specialists if required will be carried out by the Customer O M B Si...

Page 5: ...ices to use the equipment SECTION 1 GENERAL DESCRIPTION 6 Introduction to the manual technical specifications and description of the equipment s features SECTION 2 INSTALLATION OPERATION AND MAINTENANCE 13 Basic instructions for a correct installation maintenance and equipment s operation SECTION 3 TECHNICAL INFORMATION 32 Technical information about the modules including schematics and layouts ...

Page 6: ...FM Transmitter Sistemas Electrónicos S A EM 100 DIG Technical Manual v1 2 November 2005 2 S Se ec ct ti io on n 0 0 G GE EN NE ER RA AL L R RE EC CO OM MM ME EN ND DA AT TI IO ON NS S ...

Page 7: ...cement always refer to User s Manual To avoid explosion do not operate this equipment in an explosive atmosphere To avoid personal injury do not remove the product covers or panels Do not operate the product without the covers and panels properly installed GOOD PRACTICES During the maintenance of the equipment covered in this Manual please keep in mind the following standard good practices When co...

Page 8: ...the power Carefully avoid touching him or his clothing until free of power EMERGENCY RESUSCITATION TECHNIQUE Step 1 Check the victim for unresponsiveness If there is no response immediately call for medical assistance and then return to the person Step 2 Position the person flat on their back Kneel by their side and place one hand on the forehead and the other under the chin Tilt the head back and...

Page 9: ... Continue treating victim for electrical shock Check for points of entry and exit of current Cover burned surface with a clean dressing Remove all clothing from the injured area but cut around any clothing that adheres to the skin and leave it in place Keep the patient covered except the injured part since there is a tendency to chill Splint all fractures Violent muscle contractions caused by the ...

Page 10: ...M 100 DIG Technical Manual v1 2 November 2005 6 S Se ec ct ti io on n 1 1 G GE EN NE ER RA AL L D DE ES SC CR RI IP PT TI IO ON N CONTENTS 1 1 Introduction 7 1 2 General description 7 1 3 Description of panels 9 1 4 Technical specifications 12 ...

Page 11: ...to the internal pre setting other than frequency and few other options are not usually required but if they are once again they must be done by skilled personnel fitted with proper instrumentation and service documentation Improperly tampering with the settings may harm the apparatus or jeopardize the guaranteed performance THIS EQUIPMENT COMPLIES WITH ALL RELEVANT EMI EMC AND SAFETY REQUIREMENTS ...

Page 12: ...sed to remotely control the transmitter Above Figure 1 1 shows us the external view of Transmitter s cabinet whose control panel has been simplified to a maximum being Microcontroller in charge of practically to select and make all tests and adjustments of all parameters that are relevant to the normal Equipment s performance Due to this fact Front Panel has only a few control elements since with ...

Page 13: ...ments are numbered in Figure 1 2 as follows 1 STANDBY condition indicator LED 2 Twin row Alphanumeric dot matrix LCD display working directly with Microcontroller unit 3 Programming parameter selection keyboard White keyboard to scroll and navigate through the different menus and options OK key blue Enter key to confirm some order or command CANCEL key orange Escape key to cancel menu or command 4...

Page 14: ...io channels input sockets on balanced female XLR type connectors Left Right The wide band externally processed stereo composite signal input on a grounded unbalanced BNC female connector The low frequency limited 20kHz 100kHz auxiliary channel input on a grounded unbalanced BNC female connector The LF MONITOR output for monitoring RDS external synchronization or re broadcasting purpose BNC type fe...

Page 15: ...nals inverted to the port it needs a simple straight wired serial cable with appropriate connectors usually a female DB 9 or DB 25 to the PC port and a male DB 9 connector at the transmitter end Appropriate OMB software is required for communication WARNING Do not connect the serial cable with neither transmitter nor PC turned on 7 RF sample output for frequency measuring or RF signal monitoring B...

Page 16: ...OPERATING TEMPERATURES RANGE 0 35ºC recomm 10 45º C max MOUNTING DIMENSIONS W O HANDLES Width 19 height 5 1 8 Standard 19 Rack DIMENSIONS 483 mm width x 125 mm height x 334 mm depth MODULATION Frequency 75KHz peak dev MODULATION CLASS F3E F8E OSCILLATOR S SYNTHESIS STEPS 10 100KHz FREQUENCY ERROR 200Hz FREQUENCY DRIFT 250Hz over temperature 100Hz year RF OUTPUT POWER adjustable between 2 and 100Wr...

Page 17: ...ti io on n 2 2 I IN NS ST TA AL LL LA AT TI IO ON N O OP PE ER RA AT TI IO ON N A AN ND D M MA AI IN NT TE EN NA AN NC CE E CONTENTS 2 1 Introduction 14 2 2 System connection 14 2 3 Audio Base band connections and presets 15 2 4 Operation 19 2 5 Commands and programming 21 2 6 Service and maintenance 31 ...

Page 18: ...F OUT to the antenna or RF Power Amplifier with low loss 50 coaxial cable tested to 500W of peak power rating in the frequency range used Andrew LDF4 or 1 2 Cellflex line can be used in some short hops 2 Connect the audio inputs as required for operation and detailed in the following chapters for various situations If needed connect the serial and or parallel remote control I O ports as required o...

Page 19: ...ameters that may require some setting in the field the 2nd level password is enough and may be used for any standard service requirement The main purpose of the existence of the 3rd level is a security assurance for the user if he loses control on the lower password levels 7 If not already done adjust frequency and RF power as required and check reflected power on the transmitter s display To this...

Page 20: ...uency mono and stereo channel signals have to be adequately pre emphasized Standard preemphasis time constant is 50 and 75 µs the former being usually factory pre set for Europe countries Check whether this is correct for your country it is usually correct for any European country and part of the Pacific areas It is not correct for USA and Center South America standards which require 75 µs If abov...

Page 21: ...in stereo and RDS or SCA signals applied at the same time To measure only the audio channel signal go to the Left Right level menu screen The auxiliary channel level is slightly less immediate to set being measured in dB only Remember that 0dB corresponds to 7 5kHz deviation i e 10 max allowed total modulation The typical level for RDS so being 11 5 for 2kHz deviation This menu screen accounts onl...

Page 22: ...odulation dynamics and improper functioning of the limiter 2 3 4 RS232 Serial Port The RS 232 port manages only Tx Rx and Return data signals with no handshake Being the two former signals wired inverted to the port it need a simple straight wired serial cable with appropriate connectors usually a female DB 9 or DB 25 female to the PC port and a male DB 9 connector at the transmitter end Appropria...

Page 23: ...ce to transmit in monaural mode In this case the transmitter is already preset for stereo operation if needed simply reversing transmission mode to STEREO 2 Select the MODE command menu screen and select MONO L R operating mode Confirm or change also 50 or 75µs preemphasis as required 2 4 3 Mono or Stereo Broadcasting from a Radio Link Receiver or an External Encoder 1 In this case the signal is a...

Page 24: ...ion Adjustment with Broadcast SignaL Check the overall modulation level for adequacy as follows 1 Select the display menu screen MPX The total modulation will be displayed both in dB and as deviation in kHz An analog moving bar and a digital peak reading are shown at the same time 2 Send a sufficiently constant level music signal to modulator input and check that the measure hovers around 0dBm and...

Page 25: ... to navigate freely through exciter s monitoring menu information OMB suggests leaving it in this state if a high privacy level is not required If set to ON it will show the default menu screen 00 requiring password for any other information or pre set Failure to insert a correct password of any level will impede any other access to the commands for the time out length usually 3 minutes No change ...

Page 26: ...rchical tree of the menu is depicted in the following Figure 2 1 with a small number near the left side of each field for easy reference In the following pages we will examine each menu field and option All of the first column fields require the first level password authorization to be navigated In a similar way practically all the second column fields require the second level authorization as som...

Page 27: ...key input will turn this menu field on the next requesting a password code MENU 11 INITIAL PASSWORD ENTER PASSWORD CODE This screen requests to input a valid password code When the input is confirmed by the OK key the word will be compared with the memorized passwords and if recognized the corresponding security level will be allowed If the password is incorrect or the input is terminated by a CAN...

Page 28: ...FM Transmitter Sistemas Electrónicos S A EM 100 DIG Technical Manual v1 2 November 2005 24 Figure 2 1 SEQUENCE OF MENUS DISPLAYED BY SCREEN HYERARCHICAL TREE ...

Page 29: ...U 02 MULTIPLEX SIGNAL LEVEL OUTPUT MODULATION MPX 75KHz 7 1 DB ŰŰŰŰŰŰŰŰŰŰŰŰ This screen shows the actual peak modulation in dB referred to 75kHz and as deviation in kHz A pseudo analog moving bar simultaneously fast changes with the modulation leaving a peak mark at its end for 1 or 2 seconds A vertical bar on this line marks the 0dB position Command mode with the 2nd level password authorization ...

Page 30: ... to an auxiliary SCA RDS signal in dB referred to 7 5kHz or 10 of max peak modulation Usual level for SCA signal is 0dB 7 5kHz while a standard RDS modulation is set at 11 5dB 2kHz Command mode with the 2nd level password authorization permits to set auxiliary input channel sensitivity See menu 25 MENU 06 AUX LEFT RIGHT AND MPX LEVEL IN DB aux l r mpx 00 0 0 0 0 0 0 0 This screen simultaneously su...

Page 31: ... the actual data and clock To set data and clock it is required to go in command mode with the 2nd level password authorization See Menu 29 The temperature sensor is optional and when present in the case of EM 100 DIG reads the internal temperature slightly behind the front panel It is usual it reads some 20 C higher than external ambient temperature at full output power i e some 65 C assuming an ...

Page 32: ... by this condition Any attempt to access the exciter will cause the password request if an invalid password in entered it needs to wait for the time out to permit a new attempt or to remove the mains power to the equipment causing a hardware reset Even in this case the first request will be a valid password input MENU 14 SOFTWARE RESET exec sw reset yes no This screen permits to execute a software...

Page 33: ... code as in the current level which is to be changed Failure to do so will show the message ERROR PASSWORD This display stops input mode for 5 second and than permits to exit and possibly to try again with the CANCEL key MENU 25 AUXILIARY CHANNEL INPUT LEVEL SET set aux gain This screen in command mode with the 2nd level password authorization permits to set the auxiliary channels input sensitivit...

Page 34: ... to 15W for security reason Auto Control on the lower line is not operative and could be absent in other software releases MENU 32 LIMITER SET mpx limit level autocontrol This screen with the 3rd level authorization permits to set the limiter action The right left keys toggles limiter on and off The up down keys vary the threshold level Auto Control on the lower line is not operative in some softw...

Page 35: ...ce for quite some time Only periodical cooling fan heat sink inspection and fan replacement after 2 years of continuous service even if it s yet in good conditions Minimum maintenance inspection is set monthly containing the following aspects 1 Throughly clean Equipment externally Clean Equipment s room and Transmitter s environment Check that internal humidity and room s temperature not to exceed...

Page 36: ... 2005 32 S Se ec ct ti io on n 3 3 T TE EC CH HN NI IC CA AL L I IN NF FO OR RM MA AT TI IO ON N CONTENTS 3 1 Introduction 33 3 2 Main board 33 3 3 Stereo encoder optional 38 3 4 FM Exciter 41 3 5 R F Power Amplifier module 44 3 6 Control unit and display board 50 3 7 Power Supply 56 ...

Page 37: ...ts level adjustment audio pass filtering and limiting the RF control section and the I O interfaces It also interconnects the various transmitter modules with ribbon type cables Its electrical diagram is splitted in two sheets for clarity purpose they will be examined in sequence In the first Schematics sheet are situated the I O interfaces both audio and digital ports and the analog RF control Le...

Page 38: ... processed in the same channel as the right one Three buffer amplifiers follows each channel IC7a IC8a and IC12a The output of the first two amplifiers drive the pre emphasis stages whose time constants can be digitally set at 0 50 and 75µs through the analog gates of IC9 A limiter stage follows this arrangement built around D8 and D9 diodes acting as clippers By acting on the limiter s reference ...

Page 39: ...Eng Dpt EM 100 DIG MAINBOARD I O R F Control Section 1 2 3 4 5 6 7 8 A B C D 8 7 6 5 4 3 2 1 D C B A Drawn Checked Standards Date Name Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A ...

Page 40: ...MB Eng Dpt EM 100 DIG MAINBOARD LF Process Section 1 2 3 4 5 6 7 8 A B C D 8 7 6 5 4 3 2 1 D C B A Drawn Checked Standards Date Name Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A ...

Page 41: ...Date Drawn Checked Name Standards Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A 01 11 04 OMB Eng Dpt EM 100 DIG Mainboard ...

Page 42: ...ass filter follows to remove higher order harmonic products This filter is also made with highly precise active circuitry built around IC5 and IC6a b The latter section c of IC6 performs phase equalization The four analog switches comprised in IC7 permits to select the mono or the stereo encoded signal and to slightly vary the encoder gain to adjust for the 90 audio modulation in stereo vs 100 in ...

Page 43: ...1 04 OMB Eng Dpt EM 100 DIG Stereo encoder 1 2 3 4 5 6 7 8 A B C D 8 7 6 5 4 3 2 1 D C B A Drawn Checked Standards Date Name Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A ...

Page 44: ...Date Drawn Checked Name Standards Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A 01 11 04 OMB Eng Dpt EM 100 DIG Stereo encoder ...

Page 45: ...ge This latter is composed by two small MOSFET transistors TR9 and TR10 and attains some 900mW output level 29dBm over the full FM range To correctly operate TR9 and TR10 require a gate bias voltage which is factory pre set by RT1 The digital PLL circuit is entirely contained in IC2 whose frequency reference is derived by a highly precise temperature compensated oscillator TCXO1 running at 12 8MHz...

Page 46: ... 11 04 OMB Eng Dpt EM 100 DIG FM Exciter 1 2 3 4 5 6 7 8 A B C D 8 7 6 5 4 3 2 1 D C B A Drawn Checked Standards Date Name Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A ...

Page 47: ...Date Drawn Checked Name Standards Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A 01 11 04 OMB Eng Dpt EM 100 DIG FM Exciter ...

Page 48: ... AB1 common emitter design The elements contained in this module are 1 Cooling fan directed towards heat sink s cooling fins 2 Output low pass filter and directional coupler 3 RF output Power amplifier section 4 Main Power supply 6 BLF 278 MOSFET output power amplifier twin transistor capsule 7 RF output connector 8 RF monitor output Output amplifier stage detail can be seen in Figure 3 3 Fig 3 3 ...

Page 49: ...harmonics to a value that is generally below 70dBc following the output transistor drain circuit Also included in the RF output path a directional coupler 2 generates a dc signal which is proportional to the forward and reflected RF power and a RF non demodulated sample RF MONITOR to be externally used by a frequency counter or a modulation monitor for measurements purposes The transistor gate is ...

Page 50: ... X7R C17 1 Cap 47pF SMD 1210 5 500V C17 C18 1 Cap 15pF SMD 1210 5 500V C17 C19 1 Diode BAT54 SMD SOT 23 D1 D2 2 Zener diode 10V SMD 0 35W D4 1 Thread 0 8mm Cu Ag 30mm approx Material for L1 and TR2 fixing Thread 1mm Cu enamelled 250mm approx Material for L2 Thread 1 5mm Cu Ag 50mm approx Material for L5 and TR1 fixing Axial ferrite L3 l4 2 Output transformer core L5 1 22 SMD 1206 1 4W r2 r3 2 Pote...

Page 51: ... 15pF C3 1nF R5 1R 2W R6 51 R7 RF 100 Ohm R2 22 R3 22 R11 330 GND GND D2 BAT54 R4 P1K GND C4 1nF GND 12V Polarization L1 Bridge GND GND GND C6 1nF C8 150pF R9 51 R8 RF 100 Ohm GND C10 12pF GND TR2 Output Transf GND GND GND GND L2 Dext8 8turns Dcable 0 8 1 R10 10 Ohm 2W C15 100uF C16 1nF C17 22nF GND GND GND 48v GND C12 470pF C13 470pF C14 470pF GND D1 BAT54 R12 110 BIAS Off C20 1nF R13 10K D3 LED ...

Page 52: ...Date Drawn Checked Name Standards Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A 04 05 04 M Tsvelev MODPOT v1 3 300W R F Power Amplifier ...

Page 53: ...m d1 5mm TL1 50 Ohm TL4 Forward Power TL2 Monitor TL3 Reflected Power RF Out Output Coupling Monitor R11 120R R3 51R R5 1K R7 10K R9 120R R2 51R R1 51R R4 51R R6 1K R8 10K R10 120R C8 1nF C9 1nF C10 1nF C11 1nF C7 22pF C5 22pF C6 22pF D2 BAT54 D1 BAT54 C2 51pF 500V RF C1 25pF 500V RF C3 51pF 500V RF C4 25pF 500V RF C12 4 7pF 500V RF C14 12pF 500V RF C13 9 1pF 500V RF Reflected Coupling In case of ...

Page 54: ... some steady state signals are multiplexed to its input by IC3 so requiring only one peak rectifier and increasing the number of the analog channels One analog channel reads the internal temperature through the optional TR3 sensor Figure 3 5 Detailed view of Control Unit The simple specialized IC6 performs clock and date functions as a stand alone unit backed up by a NiMnh battery which keeps circ...

Page 55: ...h TR2 The alphanumeric display is a separate module connected to the board by a small flat ribbon cable as shown in Figure 3 6 above Eleven digital lines incoming from the Microcontroller drive this module The internal board potentiometer RT1 regulates the LCD contrast and may be used to change it for different situations A separate power supply current for the backlight LEDs is provided by R41 an...

Page 56: ...04 03 OMB Eng Dpt EM 100 DIG Control unit 1 2 3 4 5 6 7 8 A B C D 8 7 6 5 4 3 2 1 D C B A Drawn Checked Standards Date Name Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A ...

Page 57: ...Date Drawn Checked Name Standards Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A 18 04 03 OMB Eng Dpt EM 100 DIG Control unit Component side Solder side ...

Page 58: ...MB Eng Dpt EM 100 DIG Keyboard display interface 1 2 3 4 5 6 7 8 A B C D 8 7 6 5 4 3 2 1 D C B A Drawn Checked Standards Date Name Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A ...

Page 59: ...Date Drawn Checked Name Standards Signature Scale Title Drawing nr Replace Replaced with Sistemas Electrónicos S A 16 07 02 OMB Eng Dpt EM 100 DIG Keyboard display interface COMPONENT SIDE SOLDER SIDE ...

Page 60: ...nge transformer tap The power supply accepts mains input variations generating an unregulated DC voltage which is used by the regulator as input voltage This unit is intended to be replaced as a whole unit in event of damage and not to be repaired in the field This power supply delivers 30VDC to the load at a nominal power rate of 240W WARNING IN THIS UNIT MAINS VOLTAGE AND OTHER DANGEROUS VOLTAGE...

Page 61: ...FM Transmitter Sistemas Electrónicos S A EM 100 DIG Technical Manual v1 2 November 2005 57 INTENTIONALLY BLANK ...

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