With the SC-4 SSTV-PC-Scanconverter and the Charly 4.0-software you will be able to take part in one of the most fascinating fields of ham radio: Slow Scan Television (SSTV), the wordwide exchange of high quality color images via your computer and radio equipment.
Other popular SSTV software uses the soundcard approach to demodulate and generate SSTV. As a large number of samples have to be analyzed and processed continuously by the PC, these systems consume a large amount of processor resources, which will then be short for other tasks, like image processing, multitasking, which -if possible at all- will then be limited and slow.
On the other hand, it is very desirable to be able to do sophisticated image processing etc. while receiving and transmitting SSTV, e.g. for preparing other pictures to be sent next.
For this, a different approach is required:
"SC-4 & Charly" follows the philosophy of using powerful external hardware to relieve the computer from tasks that can better be done externally in order to achieve best performance, program speed and full multitasking capabilities. Especially under "Windows" it is favourable to have all time-critical and signal-processing tasks being done externally. The SC-4 is a fully functional microprocessor-controlled SSTV-Scanconverter, operated from the PC via the serial port. (You can disconnect the serial cable from the PC during SSTV transmission and the SC-4 will continue transmitting normally from the internal hardware buffer!). As the PC is not involved in signal processing and clock generation, there is no need for a "slant correction", only minor PC resources are used and received information will be displayed immediately without any delay. Due to a special sync-detection-algorithm in the SC-4 firmware, synchronisation is always fast and accurate. The different tasks share a microcontroller and a very fast, specially programmed LSI-chip. Thus high complexity of algorithms and fast speed of operation can be achieved concurrently at low cost. Due to the extremely high noise immunity and stability, the system will receive good images even under severe QRM or QRN conditions.