A modernized version of the famous 56 kb msk modem designed by Dale Heatherington, The WA4DSY.
Licensed by PacComm.
WA4DSY designed a 56 kb MSK RF Modem in the late 80's which has been used successfully in the Atlanta and Ottawa areas.
The modem was sold as a kit by the GRAPES club in Atlanta, and is often called the GRAPES modem.
The new design is a single pc board.
Parts count is greatly reduced.
Many tune up and operational conveniences have been added.
MUST BE USED WITH A TRANSVERTER FOR THE DESIRED FREQUENCY
Power Requirements: 12 volt at 300 ma.
Packaged in a Paccomm extruded case 7.25 wide x 7.25 deep x 1.5 high.
Optional 12 volt, 30 watt switching supply powers both modem and transverter.
THE INTERFACE CONNECTIONS
Power: 2.1 mm Round Connector.
Electrical: Balanced RS-422 or CMOS.
Physical: DA15 Female.
IF in/out: BNC.
Transverter: 5 pin DIN, Female.
THE PERFORMANCE
IF Frequency: 29-30 MHz Output.
Power: Adjustable from 0.1 mw to 2 mw.
Frequency Control: Synthesizer 1 kHz steps.
Key-up Delay: 0 ms.
RX DCD Time: 3 ms.
Total Delay: 3 ms.
THE FEATURES
Remote reset system.
Allows a remote site computer to be reset by remote control.
Built in fifo bit regenerator.
Allows the modem to become a full duplex bit repeater with no additional hardware.
The RS422 interface remains fully functional when the bit repeater is enabled.
THE WATCHDOG TIMER
A 2 second watchdog timer turns off PTT after 2 seconds.
Resets when rts goes false.
Can be disabled.
THE BUILT-IN TUNING AIDS
In tune up mode the transmitter becomes a sweep generator to allow tuning the RF coils properly using only a dual trace 30 MHz scope.
THE LED'S
Led's: Signal strength display.
Led's: Ready, PTT, and DCD.
Led: One internal led which indicates when the remote reset relay is closed.
THE SWITCHES
Front panel: power switch push on push off, rotary hex frequency selector.
Rear Panel: key tx activates transmitter and sends scrambled ones.
Remote Reset: Sends remote reset code.
THE PACCOMM WA4DSY BACK VIEW
THE TECHNOLOGY
All the digital logic is implemented in a single Xilinx XC3042A-7 chip packaged in an 84 pin PLCC.
Data carrier detection is done digitally in the Xilinx chip.
User transmit data is scrambled x17 + x5 +1 and converted to NRZ.
A 27C256 EPROM holds both the Xilinx chip programming data and all the state machine and waveform tables for the modem transmitter.
It also holds the data which is loaded into the frequency synthesizer at power up.
Transmit and receive frequencies are programmed independently.
The only adjustments involve tuning the filters.
The special tuning mode should make that task simple.
The transmitter signal is compatible with existing 56KB WA4DSY Modems.
Drive the 56kb modem with a gracilis packet win hdlc card or, for stand alone operation, a PacComm SPIRIT-2 PAD or a Gracilis PackeTen.
Gracilis Packet Win WA4DSY 56KB Modem Interfacing Instructions
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