MARTI STL-10A Transmitter (broadcast radio)

55 Pages·2001·0.817 MB·English

MARTI
ELECTRONICS
STL TRANSMITTER
MODEL STL–10A
October, 2001 597–9500
TECHNICAL MANUAL
MARTI ELECTRONICS
STL-10A BROADCAST STL TRANSMITTER
TABLE OF CONTENTS
DESCRIPTION PAGE NO.
INTRODUCTION – STL–10A 1
SPECIFICATIONS 3
UNPACKING AND INSPECTING 5
INSTALLATION 5
STL–10A TRANSMITTER INSTALLATION 5
ANTENNA INSTALLATION 6
STL ANTENNA INSTALLATION CHECKLIST 6
ANTENNA ASSEMBLY 6
TRANSMISSION LINE CONNECTOR ASSEMBLY 6
MOISTURE PROOFING COAX CONNECTORS AND FITTINGS 6
LOCATION AND GROUNDING OF COAXIAL CABLE 7
SYSTEM GROUNDING 7
ANTENNA INSTALLATION AND ADJUSTMENT 7
OPERATION 7
SWITCH AND METER FUNCTIONS 7
TRANSMIT–OFF SWITCH AND LED 7
FORWARD–REFLECTED SWITCH AND RF POWER METER 8
PEAK MODULATION METER 8
TEST METER 8
PRE–EMPHASIS SWITCHES 9
FREQUENCY MEASUREMENT 9
STL–10A PERFORMANCE TESTS 9
NOISE 10
DISTORTION 10
FREQUENCY RESPONSE 10
STL–10A THEORY OF OPERATION 10
POWER SUPPLY 800–168 10
INPUT/OUTPUT FILTER 800–193A 10
CONTROL BOARD 800–197 10
AUDIO BOARD 800–194 11
MODULATOR 800–195 11
MULTIPLIER BOARD 800–163 11
RF POWER AMPLIFIER 800–374B AND 800–373B 11
DUAL LINK STEREO STL 11
TEST EQUIPMENT 14
TOOLS FOR ALIGNMENT OF STL–10A SERIES TRANSMITTERS 14
 Marti Electronics 2000
ALL RIGHTS RESERVED
Printed in the U.S.A.
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DESCRIPTION PAGE NO.
TUNE–UP PROCEDURE FOR STL–10A 14
MODULATOR CIRCUIT BOARD 800–195 ADJUSTMENTS 14
STL–10A TRANSMITTER TEST REPORT 15
AUDIO CIRCUIT BOARD 800–194 ADJUSTMENTS 16
MULTIPLIER CIRCUIT BOARD 800–163 ADJUSTMENTS 16
RF POWER AMPLIFIER BOARD 800–374B AND 800–373B 16
ADJUSTMENTS
POWER CONTROL POT CALIBRATION 16
B+ ADJUST 17
FORWARD POWER METER ADJUST 17
REVERSE POWER METER ADJUST 17
PA CURRENT ADJUST 18
FREQUENCY MEASUREMENT 18
STL-10A PARTS LIST 22
STL-10A SCHEMATICS 33
LIST OF ILLUSTRATIONS
FIGURE NO. TITLE PAGE NO.
1 STL–10A TRANSMITTER 1
2 STEREO STL SYSTEM BLOCK DIAGRAM – 702–058 2
3 FCC EMISSION PROFILE (500 KHZ CHANNEL) DRAWING 12
4 FCC EMISSION PROFILE (200 KHZ CHANNEL) DRAWING 13
5 STL–10A TRANSMITTER BLOCK DIAGRAM 19
6 STL–10A ADJUSTMENT LOCATIONS 20
7 STL–10A MAIN FRAME 21
LIST OF TABLES
TABLE NO. DESCRIPTION PAGE NO.
1 STL–10A ELECTRICAL AND PHYSICAL 4
SPECIFICATIONS
2 STL-10A PARTS LIST 19
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WARNING
THIS EQUIPMENT MUST BE OPERATED WITH A 3–CONDUCTOR
GROUNDED AC POWER RECEPTACLE. FAILURE TO USE A
PROPERLY GROUNDED RECEPTACLE MAY RESULT IN IMPROPER
OPERATION OR A SAFETY HAZARD.
LIMITED WARRANTY COPYRIGHT NOTICE
The Seller warrants that, at the time of shipment, the
products manufactured by the Seller are free from de- 2000 All Rights Reserved
fects in material and workmanship. The Seller’s obliga- Marti Electronics
tion under this warranty is limited to replacement or re-
pair of such products which are returned to Marti at its
No part of this manual may be reproduced, transmitted,
factory, transportation prepaid and properly insured,
transcribed, stored in a retrieval system , or translated
provided:
into any language, natural or computer, in any form or
a. Notice of the claimed defect is given to Marti with by any means, without the prior written permission of
in one (1) year [two (2) years for STL systems] from Marti Electronics.
date of original shipment and goods are returned in ac-
cordance with Marti instructions. Artwork depicting circuitry in this manual is protected
b. Equipment, accessories, tubes and batteries not by copyright laws.
manufactured by Marti are subject to only such adjust-
ments as Marti may obtain from the supplier thereof. Information in this manual is subject to change without
notice and does not represent a commitment on the part
c. This warranty does not apply to equipment which
of Marti Electronics.
has been altered, improperly handled, or damaged in
any way.
Marti Electronics may make improvements and/or
The Seller is in no event liable for consequential dam-
changes in this manual or in the product described here-
ages, installation cost or other costs of any nature as a
in at any time.
result of the use of the products manufactured or sup-
plied by the Seller, whether used in accordance with in-
structions or not. This product could include technical inaccuracies or
typographical errors.
This warranty is in lieu of all others, either expressed or
implied. No representative is authorized to assume for
the Seller any other liability in connection with Seller’s
products.

PHONE NUMBERS:
MAILING & SHIPPING ADDRESS:
MARTI Electronics Sales (817) 735–8134
4100 North 24th Street Sales FAX [phone]
Quincy, Illinois 62301 Service (217) 224–9600
The United States of America Service Fax [phone]
INTRODUCTION – STL–10A.
The MARTI STL–10A Studio Transmitter Link/Inter–city Relay is a line–of–sight FM communications system pro-
viding a high quality broadcast audio channel with two optional sub–channels. A dual link for stereo provides two
identical broadcast quality channels with better than 70 dB stereo cross–talk and four optional sub–channels. These
systems offer greater rejection of interference, superior noise performance, much lower channel cross–talk, and
greater redundancy than currently available composite STL systems.
APPLICATIONS OF THE STL–10A SYSTEM (FCC Approved Parts 74, 101):
•
STL for FM stereo broadcast (dual system)
•
STL for AM stereo broadcast (dual system)
•
STL for FM monaural or AM monaural broadcast
•
Inter–city relay for linking two or more broadcast facilities
•
Multi–relay system for radio network distribution
•
Communications link between satellite earth station and broadcast
facilities
•
Data and Background Music links
•
Private microwave service
Complex systems can be built from basic STL–10A transmitters and R–10 receivers having multiple relay (repeat-
ers), bi–directional (full duplex), and automatic switching hot standby features (refer to Figure 2).
Features of the STL–10A Transmitter include:
(cid:1) FCC approved under Parts 74 and 101.
(cid:1) User selectable audio processing provides 0, 25, 50, or 75 microsecond pre–emphasis
options.
(cid:1) Low–pass filters designed to eliminate overshoot on complex audio waveforms.
(cid:1) Calibrated RF watt meter for forward and reflected power.
(cid:1) Test meter on front panel indicates Subcarrier Level, Supply Voltage, PA Current, For
ward and Reflected Power. Additional test points are located inside transmitter.
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COPYRIGHT 2000 MARTI ELECTRONICS
FIGURE 2. STEREO STL SYSTEM BLOCK DIAGRAM – 702–058
(cid:1) Automatic output power control. The power control maintains the output power to a
specific level and is independent of temperature and voltage changes.
(cid:1) Twelve segment bar graph for display of peak transmitter modulation. The five highest
LED’s (100% to 250%) have a “peak–hold” feature which will display instantaneous
peak value for one second, a valuable feature when dealing with pre–emphasized
program audio.
(cid:1) Automatic switching capability by addition of Model ATS–15E Transmitter Switcher
(cid:1) Accessory plug for external DC power, remote control, remote metering, and other
functions
(cid:1) Low power consumption for operation on AC, solar cell, battery, or other
single–polarity DC source. (Marti Model UPS–12 Uninterruptible Power System).
(cid:1) Terminal strip for a balanced 600 ohm audio input, BNC jack for unbalanced audio,
Sub 1, and Sub 2 inputs.
The Marti STL–10A system derives its excellence from Marti’s experience in supplying thousands of such systems
world–wide over the past thirty years. This equipment incorporates state–of–the–art technology and is manufactured
in modern, efficient facilities under high quality–control standards.
STL–10A System Specifications
Freq Receiver
Range Maximum Maximum IF System Specifications
MHz Transmitter Power Deviation Receiver Bandwidth Frequency Response Distortion Noise
850–960 STL––10/950 10 watts ±50 KHz R–10/950 200 KHz ±0.25 dB, 20–15000 Hz 0.25% or less –80 dB or better
System specifications shown are for 200 KHz receiver IF bandwidth. Narrow band channels requiring 85 KHz IF
bandwidth have ±0.25 dB response, 0.3% distortion.
System Applications
Freq B.W.
Range FCC Each Channel
MHz Application Part Channel Frequency Response Distortion Noise Separation
850–960 FM Stereo STL 74 200 KHz ±0.25 dB, 20–15000 Hz 0.25% or less –80 dB or better 80 dB
850–960 FM Stereo STL 74 150 KHz ±0.3 dB, 20–15000 Hz 0.3% or less –72 dB or better 72 dB
850–960 AM Stereo STL 74 100 KHz ±0.3 dB, 20–15000 Hz 0.3% or less –72 dB or better 72 dB
928–960 Data or Background Music 94 100 KHz ±0.3 dB, 20–15000 Hz 0.3% or less –72 dB or better 72 dB
928–960 4–channel Sat. Pgm. Feed 94 100 KHz ±0.3 dB, 20–15000 Hz 0.3% or less –70 dB or better 70 dB
Stereo System Differential Phase 0.5 degrees or less SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
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TABLE 1. STL–10A ELECTRICAL AND PHYSICAL SPECIFICATIONS
(Sheet 1 of 2)
PARAMETER SPECIFICATION
ELECTRICAL
FREQUENCY BAND 850 MHz to 960 MHz as specified.
MAXIMUM POWER OUTPUT 10 watts, ±0.5 watts,850 to 960 MHz.
OUTPUT CONNECTOR UG–58 (Type N Female)
OUTPUT IMPEDANCE 50 Ohms
MODULATION Direct FM
STABILITY ±0.00025%
SPURIOUS EMISSIONS More than 60 dB below carrier.
AUTOMATIC CHANGEOVER Provision for automatic changeover by addition of
ATS–15E Automatic Switcher
AUDIO INPUTS Balanced 600 Ohms, +8 dBm, barrier strip.
BNC connectors for unbalanced input.
SUBCARRIER INPUTS Two BNC connectors for remote control and/or
subcarrier inputs. 50–600 ohms unbalanced, 3 V. P–P for
10% injection.
METERING/INDICATORS Precision “Peak–hold” Bar Graph Modulation Meter.
Illuminated RF Wattmeter indicates Forward Power,
Reflected Power. Test Meter reads PA Current,
Subcarrier Level, 13.5 Volt Supply, and RF Drive 1, RF
Drive 2. LED indicates Transmit.
CONTROLS TRANSMIT switch, TEST METER switch, POWER
ADJUST Pot.
POWER REQUIREMENTS 120–220 volts ac * 50–60 Hz, 80 watts. 13.5 volt dc at
4 Amperes.
AC POWER SUPPLY Precision, electronically regulated with
current/temperature limiting.
ACCESSORY CONNECTOR 15–pin “D” connector for dc power, remote control,
automatic changeover and remote power metering.
FUSE 4 Amp Slo–Blo for 115 V operation. 1.25 Amp
Slo–Blo for 230V operation. Type 3AG.
PHYSICAL
DIMENSIONS 19 in.(48.26 cm.) wide x 3.5 in. (8.89 cm.) high x
14 in. (35.56 cm) deep.
WEIGHT Net 11 pounds. Domestic packed 18 pounds.
Net 4.9 kilograms. Export packed 8.2 kilograms.
TYPE ACCEPTANCE NUMBER FCC ID: DDESTL–10–950
(FCC PART 101 & PART 74)
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TABLE 1. STL–10A ELECTRICAL AND PHYSICAL SPECIFICATIONS
(Sheet 2 of 2)
PARAMETER SPECIFICATION
ENVIRONMENTAL
OPERATING TEMPERATURE –20°C to +50°C (–4°F to +122°F).
RANGE
* Voltage must be specified with order.
** Requires APS–28/18 Power Supply
UNPACKING AND INSPECTING.
This equipment was factory tested, inspected, packed, and delivered to the carrier with utmost care. Do not accept
shipment from the carrier which shows damage or shortage until the carrier’s agent endorses a statement of the irreg-
ularity on the face of the carrier’s receipt. Without documentary evidence, a claim cannot be filed.
Unpack equipment immediately upon receipt and thoroughly inspect for concealed damage. If damage is discov-
ered, cease further unpacking and request immediate inspection by a local agent of the carrier. A written report of
the agent’s findings, with his signature is necessary to support the claim. Check your shipment against the shipping
papers for possible shortage. Do not discard any packing material until all items are located. Small items are often
thrown away with packing material.
The packing material should be retained until equipment testing is completed. Any equipment returned to the
factory should be packed in the original cartons, insured, and pre–paid.
INSTALLATION.
NOTE INSTALL RACK–MOUNTED EQUIPMENT IN A WELL VENTI-
LATED, GROUNDED, AND SHIELDED RACK CABINET.
NOTE
Install rack–mounted equipment in a well ventilated, grounded, and shielded rack cabinet. Do not locate solid–state
equipment in a rack above tube–type equipment which produces high temperatures. Problems can also be avoided
by locating this unit away from other equipment which has transformers that produce strong magnetic fields. These
fields can induce hum and noise into the Marti equipment thus reducing performance. Strong radio–frequency (RF)
fields should be avoided where possible. Extensive shielding and filtering have been incorporated into this equip-
ment to permit operation in moderate RF environments. All equipment racks, cabinets, etc., should be bonded
together by wide copper grounding strap to ensure that all system elements are at the same RF ground potential.
STL–10A TRANSMITTER INSTALLATION.
1. Program audio output is connected to balanced audio input screw terminals. Use shielded wire. Program audio
level required is +8 dBm, 600 ohms balanced and isolated from ground. For dual channel stereo repeat
instructions at second transmitter. Audio processing requirements will be discussed in OPERATION.
2. Connect a Remote Control or Subcarrier Generator (modulator) to the jack marked “J1 SUB IN”. The subcarrier
source may be 50 to 600 ohms impedance, and the input level required is approximately one (1) volt RMS.
Subcarrier frequencies may be between 39 KHz and 67 KHz. Systems factory supplied with 200 KHz IF
bandwidths will carry subcarriers up to 92 KHz. For other subcarrier frequencies or narrow IF bandwidth
systems contact the factory. A second subcarrier generator can be connected to J3. If a dual channel stereo STL
is used connect one subcarrier generator to J1 on each channel’s transmitter.
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3. The accessory connector has several uses such as remote control, automatic switching, and external DC power.
Connection instructions are furnished with these accessories.
4. Connect STL transmitting antenna coax to “J6 ANTENNA”. This requires a type N male connector. A short
flexible jumper (20” max.) may be used between J6 and semi–flexible coax. Marti Part No. 585–017 double
shielded, low–loss RG 214/U jumper is recommended.
WARNING THIS EQUIPMENT MUST BE OPERATED WITH A 3–PRONG,
GROUNDED, 115 VOLT, AC OUTLET RECEPTACLE. FAILURE
WARNING TO USE A PROPERLY GROUNDED OUTLET COULD RESULT
IN A SAFETY HAZARD OR FAULTY EQUIPMENT
PERFORMANCE.
5. For dual channel stereo, use only Marti Part No. 585–017, 20.5 inch double shielded jumper between J6 of each
transmitter and the indicated connectors of the HRC–10B Series Combiners. Use a third Part No. 585–017
jumper between the “ANTENNA” connector of the HRC–10B and the semi–rigid coax. Refer to Drawing
702–058.
6. Turn transmitter off. Connect the ac line receptacle on back of the transmitter to a 115 volt AC power source
with special cord set supplied. Use only 3–prong grounded outlet receptacles.
ANTENNA INSTALLATION.
STL Antenna Installation Checklist.
The following suggestions are offered to help those responsible for antenna installations avoid costly errors in as-
sembly and adjustment. Marti Electronics Inc. assumes no responsibility for the installation and performance of
antenna systems associated with the equipment. The following text presents a listing of some of the most frequently
asked questions associated with the equipment. The text is not intended to be a complete step–by–step procedure.
Antenna Assembly.
Follow the manufacturer’s instructions carefully. If no instructions were included with the antenna, call or write the
antenna manufacturer for instructions. Errors are frequently made in assembly of the RF feed dipole elements which
must be installed in the same plan as the reflector grids. In other words, if the reflector grid elements are horizontal,
then the feed dipole elements must also be horizontal. Cross polarization of grid and feed dipole will result in total
loss of antenna gain.
Transmission Line Connector Assembly.
Do not use RG–58 U or RG–8 U cable for STL station antennas. They have too much loss at VHF and UHF fre-
quencies. Follow the instructions furnished by the manufacturer when cutting the coaxial cable. Inspect the cable
ends for small metal fragments which can short–circuit the line inside the connector assembly. Check the line for a
short–circuit condition after each connector is installed using an Ohmmeter. Pressurized line should be checked for
several days under pressure before installation on a tower to ensure that there are no leaks in the line or fittings.
Moisture Proofing Coax Connectors and Fittings.
Extreme care must be exercised with coaxial cable before and after connectors have been installed to ensure that
moisture does not enter the line. Foam dielectric line can absorb moisture absorption which is difficult to detect and
remedy. Therefore, keep the line dry while in storage with the ends tightly capped. Coaxial splices, connectors, and
fittings, to be located outside should be made mechanically tight, then coated with a weather–proofing material such
as SCOTCHKOTE over at least two layers of SCOTCH 88 vinyl plastic electrical tape. Moisture problems in
antenna systems are usually traced back to connectors which have NOT been properly taped. The Marti K–1
grounding and weatherproofing kit is recommended for use in each new antenna installation.
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