Broadcast Electronics 4100 North 24th Street, Quincy, Illinois 62305 USA • Phone (217) 224-9600 • Fax (217) 224-9607 • www.bdcast.com • bdcast@bdcast.com Marti GTX / GRX BROADCAST STL USER AND MAINTENANCE MANUAL Revision 1.
i GTX / GRX STL TRANSMITTER & RECIEVER Technical Manual ©2021 Broadcast Electronics all rights reserved. The information in this publication is subject to improvement and change without notice. Although every effort is made to ensure the accuracy of the information in this manual, Broadcast Electronics accepts no responsibility for any errors or omissions. Broadcast Electronics reserves the right to modify and improve the design and specifications of the equipment in this manual without notice.
ii (b) (c) (d) All computers, computer peripherals, cables, hard disk drives, etc., shall only carry the manufacturers’ or suppliers’ standard warranty in effect on their original shipment date. “Components”, defined as separate and individual parts (e.g. transistors, integrated circuits, capacitors, resistors, inductors, fans, etc.), resold by Broadcast Electronics from another manufacturer or supplier, shall only carry a 90-day warranty, effective the date of shipment.
iii IMPORTANT INFORMATION EQUIPMENT LOST OR DAMAGED IN TRANSIT When delivering the equipment to you, the truck driver or carriers’ agent will present a receipt for your signature. Do not sign it until you have: 1) Inspected the containers for visible signs of damage and 2) Counted the containers and compared with the amount shown on the shipping papers. If a shortage or evidence of damage is noted, insist that notation to that effect be made on the shipping papers before you sign them.
iv Telephone: +1 (217) 224-9617 E-Mail: parts@bdcast.com RETURN, REPAIR, AND EXCHANGES Do not return any merchandise without our written approval and Return Authorization. We will provide special shipping instructions and a code number that will assure proper handling and prompt issuance of credit. Please furnish complete details as to circumstances and reasons when requesting return of merchandise. All returned merchandise must be sent freight prepaid and properly insured by the customer.
v level has been adopted by several U.S. government agencies including the Occupational Safety and Health Administration (OSHA) as the standard protection guide for employee work environments. An even stricter standard is recommended by the American National Standards Institute which recommends a 1.0 mW/cm2 per one tenth hour average level exposure between 30 Hz and 300 MHz as the standard employee protection guide (ANSI C95.1-1982). RF energy must be contained properly by shielding and transmission lines.
vi Table of Contents General Description ................................................................................................................................................ 9 Transmitter Review ............................................................................................................................................. 11 Receiver Review ..............................................................................................................................................
vii 4.3.3 5.1.1 5.2.1 • Field #35: Synthesis setup ............................................................................................................................34 • Field #37: Ethernet & Lan setup ................................................................................................................34 RECEIVER FIELDS & MENU TREE ....................................................................................................................... 35 • OPERATION MENUS .............
viii Figures Figure 1 – GTX Transmitter Block Diagram ................................................................................................................ 11 Figure 2 – GTX Transmitter Rear Panel ........................................................................................................................ 12 Figure 3 – GRX Rear Panel ..................................................................................................................................................
9 OVERVIEW Marti GTX / GRX BROADCAST STL FAMILY SERIES VHF / UHF & SHF Bands General Description The Marti GTX/GRX series STLs are the result of experience gained by Broadcast Electronics during years of producing FM broadcast equipment, transmitters, STL and stereo encoders. These radio links were specifically designed to comply with the latest international standards and the requirements of advanced broadcasters, meeting tighter specifications than usually required, at an affordable cost.
10 The Marti GTX transmitter and its companion Marti GRX receiver are the core of a high quality, synthesized studio-to-transmitter link (STL), to be used for broadcast repeaters in conjunction with any standard FM or AM transmitter. They’re an evolution of the established Marti GTX/GRX series STL whose main circuitry is still extensively used here with a new controller, user interface and software and more advanced oscillators in a compatible 2RU, 19" case.
11 Transmitter Review The transmitter and receiver set are fitted in the same sized cabinet and are nearly identical on the front view. In fact they differ for the name on the front panel and the display and for the rear panel connector's accommodation. Both are clean and easy to control from the front panel through a single knob. The wide display and simple self-explanatory menu allows navigation through the various options.
12 Figure 2 – GTX Transmitter Rear Panel All equipment inputs and outputs but RF monitor are located on the rear panel. They are: 1. 2. The mains supply IEC320-type outlet, which incorporates the mains On/Off switch and the fuses. The internal power supply operates in 115/230 VAC mains range without any internal or external preset or switching. An additional chassis screw for system earthing and a 24V-battery backup socket pair. 3. The RF antenna connector, N-type 5.
13 Receiver Review Like the Transmitter, the Receiver front panel accommodates the single control knob, the display, four LEDs for immediate status control and a single output connector for IF monitoring. Here too regular operation is signalized by green LEDs: "PLL Lock" and "Field". This latter is a bistable and lights in yellow when RF field is too low or absent. As in the Transmitter red LEDs signals improper operation.
14 Figure 3 – GRX Rear Panel The Receiver I/O connectors on the rear panel are: 1. The mains supply IEC320-type outlet, which incorporates the mains switch and the fuses. 3. The RF antenna connector, N-type 2. 4. 5. 6. An additional earth screw for system earthing and a 24V-battery backup socket pair. The main composite signal output (Mpx+, Mpx-) on two BNC-type connectors in antiphase, permitting direct drive of two separate transmitters or one in balanced mode.
15 TECHNICAL SPECIFICATIOINS GTX and GRX Overall Data Frequency Ranges in MHz, specified on order Model Standard Freq Range (MHz) GTX/GRX200 215-270 GTX/GRX300 300-360 GTX/GRX400 400-470 GTX/GRX800 830-854 GTX/GRX900 940-960 (Other ranges on request) Alternate Range (MHz) 210-260 310-370 N/A 850-900 900-940 Modulation: FM 75kHz peak deviation. 180kF3E mono 256kF3E stereo Synthesis Step 10kHz (215 – 960 MHz) 25kHz (1.3 – 2.5 GHz) Composite Output Response: +0.1/-0.
16 Modulation Distortion @ 100% dev @ 1 kHz/ Mono ≤0.10% 0.03% typical. Stereo, 1ch ≤0.30% 0.20% typical. @ 30 - 7500 Hz Mono ≤0.25% 0.12% typical. Stereo, 1ch ≤0.30% 0.20% typical. Stereo Crosstalk: >50 dB 400 - 10000 Hz, typical >40 dB 100 - 15000 Hz, typical Input/Output: Alarm RF/LF disable, Low RF field Remote Control/Lock RS232 for Monitoring and Control Power Input Requirements: 95 / 250 VAC 50/60 Hz 22.0 - 28.0 VDC Operating Temperature Range: 0 - 35° C recommended. -10 - 45° C max.
17 Distortion, 30Hz – 15kHz: Stereo Crosstalk: Audio Response, 30Hz - 15 kHz: ±0.1dB Out of Band Audio Attenuation: <0.02% @ 75kHz dev. >50 dB (100÷5000 Hz) >45 dB (50÷15000 Hz) >50 dB @ F≥19 kHz Deviation Limiter: 0 - +7.1 dB, adjustable Composite Response: 10 Hz÷100kHz ±0.1dB Auxiliary Response: 10÷ 100 kHz ±0.2dB Power Input: 50 W max @ 90/250Vac (Po= 5W) 80 W max @90/250Vac (Po=15W) Battery Input: ≤1.8A @ 24 Vdc (Po= 5W) ≤3.0A @ 24 Vdc (Po= 15W) Dimensions, less handles: 19" 2RU, 19.0 x 3.46 x 12.
18 Distortion @ 1kHz / 100% dev. Stereo Crosstalk: Power Input: Battery Input: Dimensions, less handles: Mono ≤0.1%, 0.03% typ. Stereo ≤0.3%, 0.20% typ. >50 dB (100÷5000 Hz) >45 dB (50÷15000 15 W max @ 90/250Vac ≤0.4A @ 24 Vdc 19" 2RU, 19.0 x 3.46 x 12.
19 INSTALLATION Rack Mounting and Cooling It is very important to install the apparatus on a stable stand/rack, in such a way to permit good ventilation to the rear heatsink Since the STL equipment is cooled by convection in air, allow a 1RU clearance above and below the equipment. This especially important for heat sink in the rear of the transmitter Control Functions Both the STL Transmitter and Receiver are set and controlled by the front panel keyboard and display.
20 Pin 6, RF enable input. Base input of a common emitter transistor with a resistive pull-up. A shorted circuit to ground disables RF. Maximum voltage and current available are roughly +10V and 1mA. Pin 7, Alarm output. Open collector transistor circuit with a resistive pull-up: logic low signal means alarm condition. Correct functioning is signaled by +12V with10kimpedance. Maximum current sinking capability <10mA. Pins 4 & 9 Pins 1 & 5 Reserved for future upgrades. GRX Parallel Remote Ground.
21 We suggest using sealed batteries for small systems, 20 to 40 A/hour rated. Higher capacities, like 40 ± 100 A/hour and more, may be achieved at low cost from car-type batteries: in this case always install the batteries in a well vented place, because acid gas produced during battery charging may damage the electronic equipment. GTX and RTX battery inputs may be wired together to the same battery array, provided they both are internally set to 27.6V, as regular.
22 Table 1 – Battery Life GTX Main Consumption Backup Time with 20A/Hour Battery Backup Time with 40A/Hour Battery Backup Time with 100A/Hour Battery GRX GTX + GRX 1.95 0.45 2.4 20.5 44 16.5 9 52 ©2021 Broadcast Electronics 44 50 7.5 16.
23 SET UP For first time users of the GTX and GRX, allow some time to become familiar on how to navigate the operation and setup menus before putting the equipment into “On Air” service. Password Organization As a factory default, the equipment is delivered without any access restriction. The passwords are “OFF” in both the Transmitter and Receiver.
24 function as an "Enter" or “Select” or “Confirm” command. A longer push or “Hold” of the knob will be interpreted as an "Escape" to abort the operation. Hold the knob in for 3 seconds to ensure Escape is recognized. Refer to Figures 5 & 6, Menu Trees, and the Sample Menu below A numbering system is used in the Menu Trees to provide a quick look up of the various display descriptions, such as the #22 circled below..
25 • Field INIT: Initialization Display This field only displays when the equipment is turned on from mains power and the field is not used in other navigation. The display is very brief, typically less than 4 seconds, before advancing to the next field after. The first line of the display illuminates in a r pixel test, and then changing to the word INITIALIZING, with the model and software release displayed in the second line. The first line will then change and display an internal option(s) if present.
26 4.3.2 TRANSMITTER FIELDS & MENU TREE Operation fields #02 thru #10 are described first, followed by the Setup fields. If a field number is missing or out of sequence, the number is being used in the Receiver Menu Tree to describe a different function in the menu sequence.
27 • • OPERATION MENUS Field #02: Direct & Reflected Power Pd 20W XXXX Pr .2 W | This field shows the forward or “direct” power, Pd, and the reflected power, Pr, in the VHF models. Transmitter models in the SHF band will not show the reflected power as a circulator is used in the final RF amplifier stage in this band. • Field #04: Multiplex Signal Level (Output Modulation) MPX 75.0kHz + 0.
28 • Field #07: RDS / SCA Auxiliary Modulation Level AUX 2.0kHz -31.2dB #########O | This field shows the actual modulation for an auxiliary SCA or RDS signal in dB referenced to 7.5kHz or 10% of max peak modulation. The usual level for SCA signal is 0dB (7.5kHz) while standard RDS modulation needs to be set at -11.5dB (2kHz) • Field #09: Internal Voltages Vs2 +27.5V Vs+ +12.5 Vs-12.4 This field shows the internal regulated power supply voltages.
29 • SETUP MENUS From this menu branch, equipment parameters may be setup or changed. To enter this section and make changes, Level 2 is required. Some fields are factory set and not intended to change once the product has shipped. • Field #21: Local/Remote control setup SETUP CONTROL LOCAL & REMOTE The equipment may be controlled either locally from the front panel or remotely from the I/O lines in the rear port.
30 This field sets the main LF input channels sensitivity, i.e. multiplex, left and right channel. Note that the multiplex and right channel share the same circuitry and the sensitivity is set to the same value for all audio /multiplex channels, with a differential error (<0.2dB) at any level. Adjustment range is - 3.5 - +12.5 dBm.
31 • Field #27: Transmission Mode, and Pre-emphasis Setup MODE/PREEMPH. STEREO SETUP PR 75 μS The transmission "modes" (MONO R, STEREO, MONO L+R, EXT MPX), and the pre-emphasis timeconstants (0, 25, 50 or 75 μS) are set up here. The pre-emphasis is only active on audio channels and not an external multiplex signal. Set pre-emphasis to the correct standard for your area.
32 • Field #32: Password Management PASSWORD LEVEL 1 code=**** status=OFF This field allows status, ON/OFF and the level, 1 or 2 to be changed as well as the password itself. When a Level, or Status, or Password is changed, it is always required to confirm the correct password for that level: For example, we will change the Level 1 status to On by positioning on the word OFF, then rotating knob to change from OFF to ON. The following request for password is displayed: ENTER PASSWORD ....
33 • Field #33: Alarm Setup and Display This menu shows the various alarm conditions which are associated with the general alarm line, either located the front panel LED and the remote I/O signaling line. Some of them may be edited for their threshold level while others are factory set and fixed. The following table lists all them: • ALARM SETUP • TEMPERATURE: ON • PLL UNLOCK: ON • HIGH VSWR: ON • LOW POWER: ON/OFF • NO MODULATION: ON/OFF • OVERMODULATION: ON/OFF • TEMP. AMBIENT: 55°C TEMP.
34 • Field #35: Synthesis setup SYNTHESIS SETUP 10kHz This field displays the synthesis step frequency and can be selected,10 or 25kHz • Field #37: Ethernet & Lan setup Field #37 is for the ETHERNET & LAN hardware option. The control and display software will have this ready for the option in both the Transmitter and Receiver. Ethernet settings, IP, Mask and Gateway may be changed in this field.
35 4.3.3 RECEIVER FIELDS & MENU TREE The Receiver Menu is structured similar to the Transmitter Menu. Many of the field details have already been described in the Transmitter section and may not be listed here. Some field numbers may be listed again when additional or separate information is provided.
36 • • OPERATION MENUS Field #02: Receiver Frequency Rx #0 232.500MHz t=-01.7kHz F= -52dBm This display shows the frequency, the tuning of the received signal (T) in kHz with respect to the nominal frequency within just over ± 100kHz and the field strength (F) in dB. In the absence of received signal (Sin <-90dBm) the tuning indication is random. The signal is properly tuned when "TUNING" is within ± 6.0 kHz.
37 L########### O | R######### O | Fields 05 & 06 are only displayed if the optional internal stereo decoder is present. Field 05 displays the peak levels in the decoded audio signal on the left and right channel, expressed in dB relative to 75kHz deviation. Field 06 shows the same information with the analog bar meters. • Field #08: Stereo Pilot Frequency level PILOT TONE LEVEL DEV. 7.5kHz -20.0dB Again, this field only displays in presence of the optional stereo decoder board.
38 In this field, the user may vary the insertion level of the muting circuit and its intervention. Suitable levels are -70 to -80dBm for stereo signals and -85 to -90dBm for mono signals, depending on the received signal strength. The muting level is unrelated to the field alarm level which may be set differently by its own menu (see alarm setup, menu #33) By setting "ON" or "OFF", the muting circuit may be enabled or disabled either by "mistuning alarm" or remote control function.
39 • Field #33: Alarm setup and display As in the transmitter this field displays the various alarms that sum up to the general alarm signal, and allow some changes to them. The following table lists the alarms for the receiver: • • • • • • • • • • • • ALARM SETUP TEMPERATURE: ON PLL UNLOCK: ON LOW RF INPUT: ON/OFF MISTUNING: ON/OFF NO MODULATION: ON/OFF OVERMODULATION: ON/OFF HIGH TEMPERAT.: 55°C LOW RF INPUT: -xxdBm NO MOD. LEV.:-15.9dB NO MOD.
40 • Field #36 Left & Right Level LEFT & RIGHT LEVEL Nom: 60.9% + 6.0dBm This field displays based on the advance stereo decoder card option detected. With this option, it is possible to vary the output level of the stereo signal on the decoded rear outputs in steps equal to or less than 0.1 dB over almost the entire range between -8.4 and +12.0 dBm. The percentage does not refer to the output level but to the position of the internal electronic attenuator which has 256 steps.
41 SERVICE & CHASSIS DIAGRAMS Service and repair is limited to the overall mechanical and module interconnect wiring of the GTX and GRX. The following diagrams are provided for module and sub assembly identification of replacement modules if needed and the units cannot be returned to the factory for service.
42 Transmitter Drawings 5.1.
43 Receiver Drawings 5.2.
