PAGING BASE STATIONS
(Source: Motorola, author unknown)
The low power transmitters are fully solid state. The high power transmitters are mostly solid state except for the power amplifiers, which used tube technology for the final PAs. Transmit and receive frequencies are crystal controlled and not synthesized across the band They also require channel element changes and retuning for frequency changes. The stations still available operate in both wireline and link receiver control.
Both indoor and outdoor cabinets are available and require both rear and front door access for installation and servicing. The internal component assemblies typically have a grey or silver finish. The stations typically are referred to as one of two type, either UNIFIED or NON-UNIFIED, describing the control chassis mechanics. The unified control chassis houses control, receiver, and transmit exciter circuitry. The non-unified control chassis houses only the control circuitry, the receiver and transmitter exciter are separate components. The control chassis is a modular design with various control cards, which are interconnected by a connectorized backplane. Two separate backplanes exist, one for the unified chassis and one for the non-unified chassis. All connections to the backplane are made by either screw terminal, bubble pins or specialized connectors. Control cards are the same for both unified and non-unified stations. The stations are fully factories assembled and tested for analog and binary operation. The delay line option if ordered is a drop ship item and installed in the field. The passive delay line is manufactured by Allen Avionics and ranges in delay from 0- 1100 microseconds, adjustable in 5 microsecond steps. The paging modem is also a drop shipped item, which is installed in the field. The modem converts incoming FMK audio paging tones into RS232 level digital signals, which are then used to modulate the transmitter as FSK-NRZ data.
The paging modem is a Bell 202T type modem, which uses 1200, & 2200 Hz modem tones. The recommended modem is manufactured by Universal Data Systems, a Motorola owned subsidiary. The original manufactured modem has since been redesigned to new model, which can only be, identified by its small size. In addition to being smaller the new modem is much faster in passing data as compared to the old modem. In the event an old modem is replaced with one of the new small modems, it will have to be slowed down by using a QRN4612 modem delay module. This is required for simulcast compatibility.
Micor stations were manufactured in both simulcast and non-simulcast models. For non-simulcast models the paging synthesizer and delay lines were not required. The stations are designed for receiver flat audio, the transmit audio can be either flat or pre-emphasized. Early analog paging systems used pre-emphasis in the stations for voice paging, however this function was moved to the paging terminal and the base station transmit audio path is predominantly ordered with flat transmit audio. For simulcast systems it is much better to pre-emphasize the audio once at the source than have all stations pre-emphasizing the audio independently.
The Micor PURC paging stations come standard with Paging Universal Remote Control (PURC), a Tone Remote Control format for transmitter keying in the analog and binary mode. Depending on the type of station ordered, simulcast or non-simulcast, the paging synthesizers and delay lines will be optional. Power supplies and PA decks will vary depending on the frequency band, power out, and desired AC line voltage option. Figure 6 illustrates the general structure of a Micor PURC paging station for a Unified and Non-Unified chassis.
Micor Unified and Non-Unified Transmitter Block Diagrams
The new integrated control chassis replaces several existing station components as well as adding new features previously unavailable with Micor stations. The control tray has a built-in Bell 202T paging modem, which comes standard with the tray. An optional digital wattmeter and delay line can be ordered for full station capabilities. The DRC option with digital delay line will replace the existing UDS 202T modem and passive Allen Avionics delay line. The digital delay line has over twice the range, 2555 microseconds versus 1100 microseconds, of the Allen Avionics delay line. The DRC option requires the station to have transmit flat audio for proper operation. Stations without transmit flat audio must be upgraded prior to installing the DRC option.
The Micor DRC option uses DRC 1 messaging. The new control option allows for positive control, increased sector paging, individual station testing, and station diagnostics for alarms and forward and reflected power readings (when equipped with a digital wattmeter). The option also is compatible with Motorola dial-up diagnostics, which operates with an IBM PC or compatible when equipped with a Hayes 212 modem or equivalent. The station can be controlled by either a DDC or ASC 1000. The DRC option has a software upgrade allowing it to have the wattmeter delay line board parameters remotely controlled manually. The software upgrade works with an Enhanced DDC or an ASC1000. The Micor DRC option is available as a field retrofit kit for both Unified and Non-Unified stations through the Advanced Control Micor FMK kits.
The DRC option is not compatible with monitor receiver, time out timer, or voice actuated response (VAR) as supported with Micor PURC stations. The option is compatible with Low Band, VHF, and UHF stations, both high and low power. The option is not compatible with 900 MHz Micor stations due to a mechanical incompatibility with the 900 MHz PA deck and the control tray folding out for alignment. Electrically the DRC option will work in a 900 MHz Micor station however installation, alignment and servicing will be quite inconvenient. The product was never intended to operate with 900 MHz stations since PURC 5000 900 MHz stations are simulcast compatible with Micor and the Micor 900 MHz station was intended to be cancelled. Figure 7 illustrates the option as installed in a Micor station.
Micor DRC as Installed in a Unified and Non-Unified Station
The Micor DRC option is made up of 4 primary PC boards, in addition to the two backplane boards, one for unified and one for non-unified stations. The DRC control module is actually made up of two boards, a Control Processor Board (CPB) which handles all the logic interface to the rest of the control tray, and a Modem board which processes incoming DRC audio as well as generating DRC audio for diagnostics. The Micor Paging Control Board (MPC) performs transmit audio processing and supervises overall control tray operation and interface with the station. The digital wattmeter and delay line board function is self-explanatory.
MICOR ADVANCED CONTROL
The Advanced Control Option for Micor station is offered as a field retrofit kit only. The tray is interfaced to the Micor station using the Micor DRC backplane, Unified or Non-Unified, depending on the station type. The tray is mounted towards the bottom of the station. The space evacuated by the UDS modem and Allen Avionics delay line is utilized to provide room for the Advanced Control Tray. The Paging synthesizer is relocated to the space formerly occupied by the modem and delay line, and the Advanced Control Tray is mounted in the location where the paging synthesizer originally was. See the Advanced Control Retrofit for Micor PURC Paging Stations manual, part number 6881127E15 for detailed application information.
Advanced Control Tray Hardware Block Diagram
The Advanced Control Tray is microprocessor controlled and uses Digital Signal Processing (DSP) for audio processing. The tray is a 19-inch rack mount stand-alone. The control tray is made up of 4 printed circuit boards, the Advanced Control Board (ACB), the Power Supply Line Interface Board (PSLIB), the Display Board, and the Backplane board. The backplane board is fastened to the tray and the ACB and PSLIB board plug into the backplane. The backplane board provides connectorized interface for the tray modules as well as interface to the rest of the station hardware. The display board physically snaps into the front panel and plugs into the ACB board via a ribbon cable. The display board is made up of an 8 character alphanumeric display, 8 status and indicator LED's, and a 16-function keypad for locally operating, programming, and aligning the station. The front panel flips open for servicing of the ACB and PSLIB board.
The ACB board performs control audio processing, synthesizer programming, transmit audio processing, and station and system level alarm recognition and reporting. The board contains no user adjustable potentiometers. Board status, configuration, and alignment are accomplished via the display board display and keypad. The PSLIB board generates +5 volts for use by the logic circuits, from station supplied +13.8 and +9.6 volt supplies. Filtered +13.8VDC and +9.6VDC are passed through the PSLIB board to the ACB board for use by the audio processing circuits. The PSLIB board also contains phone line interface circuitry for wireline control stations. The tray is also available with an internal dial up/dial out modem with battery back-up and charging for diagnostic messaging. If ordered the modem is mounted piggyback on the PSLIB board. The batteries mount to the control tray cover above the PSLIB board. The tray comes with a wiring harness for interface to the rest of the station and the outside world
PURC 5000 STATIONS
The PURC 5000 family of paging transmitters are available in both indoor and outdoor cabinets. The station hardware and cabinet design have been reduced in size compared to the Micor transmitters. Station installation and servicing only requires single side access from the front of the station. All antenna, power, and control connections are made at the side of the station via the station J-box. This type of design allows the stations to fit flush against a wall or mount back to back in congested sites. Most stations can also be stacked one on top the other. The 300 watt 900 MHz station is the only exception, due to the PA and power supply requirements. The 300 watt 900 MHz. station comes in either an indoor or outdoor cabinet and requires both front and rear access. All internal component assemblies either slide out on rails or fold out for servicing. The internal component assemblies are painted with a black finish.
Non-Simulcast PURC 5000 stations come standard with Tone Remote Control, wireline control, a built in Bell 202T paging modem, minimum size required indoor cabinet, 120 V 60 Hz AC power supplies, cooling fans (depending on the make and model), RF tray and control as shown minus the wattmeter/delay line, one or two PA decks depending on the power output, and a Low Pass Filter. Simulcast PURC 5000 stations come standard with all the non-simulcast station features plus a Paging Synthesizer for increased TX frequency stability. Additional ordered options include a link receiver for RF control, digital wattmeter option for power out monitoring, digital delay line for simulcast equalization, second expansion tray for special applications using wildcards or RS232 communications, double and triple circulators, international power supplies capabilities, battery back-up options for stations, Diagnostic Metering Panel (DMP), alternate cabinets, outdoor models or dual access Micor type cabinets, and Digital Remote Control. See Figure 9 for a visual representation of the PURC 5000 station.
PURC 5000 STATION BLOCK DIAGRAM
PURC 5000 Paging Transmitter Block Diagram - Simulcast Models
PURC 5000 CONTROL TRAY
The control board slot can be occupied by either a TRC board or a DRC board pair. These control boards are microprocessor based and process both logic and audio information. The control boards continuously monitor incoming audio to the tray for control messages. The control boards do not process transmit audio. They exclusively perform control audio demodulation and via the muxbus to tell the Station Control and PURC board the mode of operation. TRC control provides no station transmitted diagnostic information, but DRC control does. DRC control allows for diagnostic messaging over-the-air or via the station line 2-wire line. The control boards contain line 1 interface and line 2 driver circuitry for phone line interface. See Figure 10 for an exploded view of the control tray.
PURC 5000 Control Tray Hardware Block Diagram
First Expansion Tray
The PURC board is a microprocessor-based board responsible for processing analog and binary paging information. The PURC board monitors incoming station audio and will process analog voice or tone pages, or convert FSK modem tones to logic levels for binary paging. The PURC board controls the analog deviation (nominal and maximum) and binary deviation alignment for non-simulcast stations. The PURC board also has responsibility for supervising the wattmeter delay line board operation. The PURC board contains wattmeter look up tables for the various frequency bands. The look up tables are stored in program prom, therefore the code will vary from board to board, depending on the station frequency band and type of wattmeter element. The board firmware has several SP versions available for the various bands to operate in a Key on Data mode for binary only systems. The board can also be jumpered to pass TTL or RS232 external paging data for applications where the internal paging modem is not needed.
The wattmeter delay line board is equipped with a three-digit seven segment display to provide the user with visual information regarding station forward power output, reflected power and a calculated VSWR, when the station is equipped with a wattmeter element. The wattmeter option also allows the user to set alarm trip points when the forward power falls below the forward alarm set point or the reflected power rises above the reflected alarm set point. The display is also used to show numerically the station settings for the digital delay line. The digital delay line has a maximum delay of 2555 microseconds in 5 microsecond increments. The clock circuitry can be jumpered from 100 kHz to 200 kHz thereby changing the resolution to 10 microsecond steps. The total board delay is then doubled to 5110 microseconds. The change in clock rate degrades the delay line audio performance and should not be used for voice paging applications. The degradation can be tolerated by binary only paging systems running GOLAY or 512 POCSAG paging. Usage with 1200 baud POCSAG is not recommended. The wattmeter digital delay line board contains audio gain and attenuation circuitry ranging from -6.4 dB to +6.2 dB in 0.2 dB steps. This board capability is only used for DRC stations equipped with remote gain and delay adjust.
Second Expansion Tray
For PURC 5000 stations there exists an IBM PC based program which will display the station muxbus and allow the user to read forward and reflected power from a station equipped with a digital wattmeter. The feature requires the station to have a second expansion tray which houses a wildcard module and an RS232 interface module. The station must also be equipped with an external auto answer Hayes compatible modem that runs at 300 or 1200 baud and must be connected to a dial-up phone line. The PC must also be connected to a Hayes compatible modem that runs at 300 or 1200 baud and be connected to a dial-up phone line. With this hardware in place the user can dial-up a station and monitor transmitter muxbus bus information in real time. The various keying modes can be deduced from the muxbus bit status. Power readings will be displayed numerically and a VSWR calculation will be made when power readings are requested.
PURC 5000 Tone Remote Control
PURC 5000 Digital Remote Control
For additional station communication features a software upgrade is available. This version is referred to as "Enhanced DRC" software, which allows the user to modify the wattmeter delay, line board settings remotely. The upgrade option is typically referred to as the "Remote Delay, Gain and Frequency Adjust" option. The software upgrade is made to the DRC CPB board and the PURC Board. New proms are required as well as adding an EEPROM to the PURC board so wattmeter delay line board settings are preserved in non-volatile memory. The upgrade also requires the DDC controller to be upgraded to Enhanced DRC operation with a software version of 2.X (the X merely indicates the latest release and any upgrades). The software upgrade can be factory installed or upgraded in the field with the appropriate retrofit kit. The field retrofit kits are frequency sensitive since the PURC board contains wattmeter look-up tables, which are not the same for all frequency bands and elements used in production. The Enhanced DRC software package allows the user to read and modify the station delay line setting, change the power alarm trip point thresholds, control station audio gain from -6.2 dB to +6.4 dB, and adjust transmit carrier frequency from 30 to 200 Hz depending on the frequency band of the station. The remote frequency adjust capability requires the station to have a paging synthesizer which has been modified to support this feature. In addition the user can remotely control 4 output wildcard bits for controlling third party site equipment.
PURC 5000 Advanced Control
The tray is made up of 4 standard PC boards and an optional dial-up dial-out modem with battery backup for dial-up diagnostic capabilities. The ACB board is the main control board responsible for interface and control of the rest of the station. The ACB board contains all the audio and binary processing circuitry. The PSLIB board is a Power Supply Line Interface Board, which generates local +5V for the tray logic circuitry. In addition the PSLIB provides interface for telephone line connects for incoming and outbound audio. The PSLIB board also supports the internal station dial-up dial-out diagnostic modem (optional) with battery backup.
Both the ACB and PSLIB boards plug into a backplane board for easy field replacement. The backplane is screwed down to the metal tray enclosure and requires no service accesses. All interface cable connections are conveniently made from the front of the backplane board. The tray is sloped down towards the back allowing easy access to interface connectors. The Advanced Control Tray comes with an interface cable harness specially designed to minimize cable clutter. The Advanced Control Tray design no longer requires the tray to slide out on rails thereby reducing the risk of pinched cables as with the PURC 5000 control hardware in Figure 10. As mentioned before all tray programming and station local access is accomplished via the Display board. See Figure 11 below for Advanced Control tray pictorial representation.
Advanced Control Tray Hardware Block Diagram
Advanced Control in PURC 5000 stations is only compatible with Simulcast stations. The tray does not support local alignment of binary deviation for Non-Simulcast stations as the PURC 5000-control hardware of Figure 10 does. All binary deviation alignment is performed in the paging synthesizer tray for Advanced Control applications. Paging operators use primarily simulcast systems and the required design effort to support Non-Simulcast stations was deemed impractical. Customers desiring Non-simulcast transmitters with Advanced Control will have no choice but to purchase a Simulcast transmitter at the additional cost of the paging synthesizer hardware.
The Advanced Control Tray is currently offered with DRC control only, TRC control is currently under development. The tray supports both DRC 1 and DRC 2 messaging standard unlike the PURC 5000 standard DRC which only supports DRC 1 messaging. The tray also includes standard digital wattmeter hardware, digital delay line hardware, RS 232 interface hardware, and wildcard input and output hardware. The digital wattmeter and delay line options are still paid for options. Even though DRC is the only control format currently supported by Advanced Control it too is a charged option. When TRC development is completed it will be the standard shipping control unless the DRC option is ordered. Consult the Advanced Control users manual, part number 6881084E80, for complete detailed tray operation. Consult SMR-5861 for hardware schematics and troubleshooting information.
|END OF SECTION|
|Home Page||Directory||Consulting||Newsletters||Free Subscription||Products||Reference||Glossary||Send e-mail|