the paccomm wa4dsy - front
PACCOMM WA4DSY 56KB MSK RF HIGH SPEED GRAPES 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.
MUST BE USED WITH A TRANSVERTER FOR THE DESIRED FREQUENCY
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 2 mW. 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.
LED'S
Ten LED signal strength display. LED's 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.
the paccomm wa4dsy - back
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
PackeTwin HDLC card or, (for stand alone operation), a PacComm SPIRIT-2 PAD or a Gracilis PackeTen.
Gracilis PackeTwin WA4DSY 56kB Modem Interfacing Instructions | 
