Transceiving CW and RTTY (RadioTeleTYpe) with the Small Wonder Labs DSW-XX and DSW-II-XX series rigs, by William K. Mabry, N4QA. Updated 17 October 2004 For this project, I am using an original DSW-20 (the DSW-II-20 is also CW/RTTY-capable, with proper modification), a homebrew hardware interface circuit, and an IBM ThinkPad 600E PC running MMTTY Ver1.65 by Makoto Mori, JE3HHT. Also required is 'DSWMULTI' software which is being developed by myself. To be successful at duplicating this project, a user must become proficient in the operation of two Windows applications which are run concurrently: 1) MMTTY Ver1.65 or equivalent software which manipulates the PC's serial port for RTTY FSK & T/R functions. MMTTY also performs RTTY demodulation and display functions. 2) 'DSWMULTI' or equivalent software which manipulates the PC's parallel printer port for DSW operating frequency and mode control functions. NOTES: Permanent physical modification of the main circuit board of the DSW-20 or the DSW-II-20 is required for this project. Persons who perform any of the following modifications do so at their own risk. If any of the following does not seem to make sense for the DSW board which you have, simply do NOT proceed. Some of the required modifications are described in step-by-step fashion. Others are left to the imagination... While the 20-meter model is used in the inaugural issue of this project, similar modifications, done to the 80, 40, and 30-meter models, will work also, now that my DSWMULTI software includes those models. There is even talk of a possible 17-meter model of the DSW-II-series. Original DSW-20 main board (circa 1999-2001): De-solder capacitor C111, remove it, and re-install it in the same holes, but from the bottom side of the board. Keep in mind that sufficient clearance must exist between the re-mounted C111 and your rig's enclosure bottom. There are two circuit traces which pass between C111's mounting holes on the top side of the board. Sever only the trace segment (at its midpoint) which connects to U4(the DDS chip), pin 10. DDS, pin 9 is the pin at the corner of the DDS nearest C111. DDS, pin 10 is the next pin over. Gently scrape each end of the now-severed circuit trace, exposing about one millimeter of bare copper. Tin the exposed copper ends. Solder a flexible, small (22 AWG or smaller) wire to each trace end. These two added wires should be long enough to reach external modification circuitry. Alternatively, these wires may be routed to an added rear-panel connector for interfacing with external circuitry. Strain-relief for the purpose of preventing damage to the circuit trace(s) is a consideration here. Newer DSW-II-20 main board (manufactured beginning in 2003): De-solder crystal Y5, remove it and re-install it in the same holes, but from the bottom side of the board. Keep in mind that sufficient clearance must exist between the re-mounted Y5 and your rig's enclosure bottom. Sever only the segment of circuit trace which passes along the edge of the silkscreen outline for Y5 nearest C23 on the top side of the board. Gently scrape each end of the now-severed circuit trace, exposing about one millimeter of bare copper. Tin the exposed copper ends. Solder a flexible, small (22 AWG or smaller) wire to each trace end. These two added wires should be long enough to reach external modification circuitry. Alternatively, these wires may be routed to an added rear-panel connector for interfacing with external circuitry. Strain-relief for the purpose of preventing damage to the circuit trace(s) is a consideration here. See my interface diagram at http://www.n4qa.com/dswmulti/dswmulti.jpg for DSW to PC interconnection details. There are two, very tiny surface-mount components used in the DSWMULTI project. Listed below are manufacturers and suggested vendors for the parts AND for surface-mount to SIP/DIP adapter boards which make breadboarding the modification hardware much easier: Manufacturer Vendor/part number Fairchild Fairchild NC7NZ17K8X (available via Fairchild's free samples program) Omega Research Limited Saelig Co, Inc. p/n DIL16 (SMT adapter board for the Fairchild NC7NZ17K8X) Pericom Pericom PI5C3303TX (available via Pericom's free samples program) Capital Advanced Technologies, Inc. Digi-Key p/n 33206CA-ND (SMT adapter board for the Pericom PI5C3303TX) How the DSWMULTI project software/hardware combination works: In DSWMULTI, frequency data are stored to the DSW's onboard Direct Digital Synthesis chip in the same manner as that in the DSWTUN03 project software, namely via Printer port pins 1(FSYNC), 4(SDATA) and 5(SCLK). The DSWMULTI mode-select output bit appears at printer port, pin 3 and drives the control input of the 'Mode Switch', which is a Pericom PI5C3303TX bus switch. 1) CW mode: This is the DSW's native mode of operation and is selected by clicking on 'CW' in the DSWMULTI window. The DSW may then be keyed via paddles, as usual. Transmit frequency data are stored in the DDS' FREQ1REG and receiver local oscillator frequency data are stored in the DDS' FREQ0REG. 2) RTTY mode: This is the mode which I've added to the DSW's mode arsenal and is selected by clicking on 'RTTY' in the DSWMULTI window. For transmitting RTTY, the DSWMULTI software stores mark and space frequency data within the DSW's onboard DDS' FREQ1REG and FREQ0REG, respectively. The MMTTY software causes the DDS to toggle between these two frequencies, during transmit intervals, via the hardware interface between the DE9 serial port, pin 3(TXD) and the DDS chip, pin 10(FSELECT). For receiving RTTY, the DSWMULTI software does not disturb the transmit mark frequency data in the DDS' FREQ1REG, but restores the DSW's normal receiver local oscillator frequency data to the DDS' FREQ0REG. Accordingly, in RTTY mode, the DSWMULTI software receives the 'T/R' data bit from the MMTTY software, via the hardware interface between the DE9 serial port, pin 7(RTS) and the DB25 printer port, pin 10(nAck) and, from this data bit, determines whether to store transmitter space frequency data or receiver local oscillator frequency data within the DDS' FREQ0REG. The DSW's internal keyer must remain in 'SK' mode while running RTTY. Below is a partial list of DX entities, Canadian provinces, and US states which I have contacted, from here in Pulaski County, Virginia, while using the DSWMULTI project. RTTY CW Colombia Costa Rica Barbados Netherlands Antilles Mexico Venezuela Honduras Panama Little Cayman Island Aruba Brazil King George Island (South Shetlands) Scotland Argentina Most Canadian provinces Dominican Republic Most US states Madeira Island Paraguay Puerto Rico Germany San Andres Island Croatia Venezuela Asiatic Russia Spain Turks & Caicos Is. Chile Scotland Poland Italy Japan Belgium New Zealand Nevis Island Greece ... Special Event Station SX1O for the 2004 Olympic Games in Athens... Chimana Island Slovak Republic Cuba England US Virgin Islands Denmark France Ecuador Faial Island (Azores) Norway Netherlands Ireland Nova Scotia New Brunswick Quebec Ontario Saskatchewan Alberta British Columbia Missouri Minnesota Louisiana Alabama Florida Tennessee New York Vermont Arkansas Texas Wisconsin Rhode Island Maine Iowa Illinois South Dakota Arizona Connecticut Oklahoma Colorado Idaho Kansas California Oregon Massachusetts Washington Wyoming Mississippi Delaware Alaska Michigan Maryland Ohio Pennsylvania Indiana Georgia Nevada New Jersey Utah Nebraska New Mexico All above contacts made using DSW-20-RTTY/CW rig and DSWMULTI software/hardware interface. Power out is 1.5 Watts. Antenna is end-fed wire, approximately 80 meters in length, and approximately 5 meters above ground. More to follow... I have no connection with any above-mentioned vendor.