The
NEW
WA4DSY 56kb RF Modem

A modernized version of the famous 56kb MSK modem designed by Dale Heatherington, WA4DSY. Licensed by PacComm.

WA4DSY designed a 56kb MSK RF modem in the late '80s 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.

This modem must be used with a transverter for the desired frequency band.

• Power requirements: +12 VDC @ 300mA.
• Packaged in a PacComm extruded case 7.25" wide x 7.25" deep x 1.5" high.
• Optional 12 volt, 30 W. switching supply. (Powers both modem and transverter).

Interface Connections

• Power: 2.1mm Round Connector
• Electrical: Balanced RS-422 or CMOS
• Physical: DA15 Female
• IF in/out: BNC
• Transverter: 5 pin DIN, Female.

Performance

• IF Frequency: 29-30 MHz
• Output Power: Adjustable from 0.1mW to 2mW
• Frequency Control: Synthesizer 1 kHz steps
• Key-up Delay: 0 ms
• RX DCD Time: 3 ms
• Total Delay: 3 ms

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.
• Watchdog Timer
  • A 2 second watchdog timer turns off PTT after 2 seconds. Resets when RTS goes false. Can be disabled .
• 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.
• LEDs
  • Ten LED signal strength display. LEDs for READY, PTT, and DCD. There is 1 internal LED which indicates when the Remote Reset Relay is closed.
• 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.
• 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 NRZI.

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 PacComm SPIRIT-2 PAD.

Pricing Information

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Any questions regarding this page should go to sales@paccomm.com
Last updated: 7/19/2004