Last updated: April 18, 2001
for
SSTV & PSK31
Quite a lot of softwares / sharewares are now available for SSTV, RTTY, Packet, Fax and PSK31 etc. Some of these uses the sound card of a personal computer as D/A converter. All we need is just a simple interface to connect the PC to our transceiver. I am now testing the below simple to build interface for SSTV and PSK31 and am having great fun in Chai Wan. Come and join us at our temporary frequencies 144.350MHz (FM mode). The circuit is still under testing, please let me know any possible problems (especially using SSB and high power).
With your creativity this interface can have some other usages:
1. Recording message received - to replay hard to copy message, especially useful in pile up situation
2. Connecting to PC for DSP, AF Spectrum and CW decode softwares
3. Transmitting message from recording device - like calling CQ for telephony and SSTV or sending standard message during contest
4. Transmitting message from sound device - like using morse code oscillator to have tone modulated CW (eg. F2A) QSOs
5. By connecting the transceiver's Manual Key to the PTT connection of the interface, this allows computer operated CW transmission (popular in contest softwares)
The second schematic is an updated circuit. It incorporates better transceiver / PC isolation by using transformers and optocoupler. It also has an additional mic connectiont which will be cut off during SSTV transmission. That allow me to keep connecting the PC at all time without the trouble of mixing computer sound to my voice QSO or mixing voice to SSTV transmission due to parallel connection.
Schematic
References
Building an Interface for PSK31 and SSTV by K4ABT
Sound Card to Transceiver Interface by K4ABT and BUX CommCo
Sound Card Interface
Connector References by BV2KS
| RS-232 Pins | DB9 | DB25 |
| RTS | 7 | 4 |
| DTR | 4 | 20 |
| GND | 5 | 7 |