The history of SCS
Two German radio amateurs (Ulrich DF4KV and Hans-Peter DL6MAA) initiated
the PACTOR® project. As early as 1986, experiments with modified
AMTOR/SITOR protocols began. In tedious tests, the noise conditions
on the HF-Bands were investigated, and the best transmission parameters
were determined. Additionally, a lot of mathematical calculations
and simulations were performed, the PACTOR® protocol deduced from
The first PTC's were wire-wrapped on bread-boards. Hans-Peter built
his PTC based on a SMD Z80 single-chip processor, while Ulrich
wire-wrapped his PTC in conventional Z80 technology. The third
station that got on the air using PACTOR® was Tom (DL2FAK). His PTC
was based on DL6MAA's SMD Z80 version. Tom and Hans-Peter ran a
lot of tests that resulted in considerable improvements over PACTOR®.
In the fall of 1989 Tom developed a PT-link system that facilitated
access to Packet-Radio nets from PACTOR®. Tom also took on the
difficult task of a project manager to coordinate the various
proposals, comments, and critiques that came pouring in, Hans-Peter's version
was too difficult for home construction, and Ulrich's version contained
too many parts. Thus, the decision was made to develop a completely
new hardware design.
Peter (DL3FCJ) developed the digital section of this hardware, Hans-Peter
developed the modem and carried out software adjustments. The
software was rounded off with inclusion of an RTTY and AMTOR routine
developed by Ulrich. Martin (DL1ZAM) revised the circuit diagram and produced
the printed-circuit-board layout. Thus the first well known PTC
was created and quickly sold all over the world.
At that time, SCS was founded.
In 1993 the production of the Z80-STI peripheral chip, used in
the Z80 PTC, ended. This created the opportunity to develop the
PTCplus. Based on an MC68000 processor, the PTCplus is the springboard
to a totally new dimension in modern HF communications.
Together with the PTCplus, the development of the PTC-II was also
undertaken. The PTC-II project required a thorough knowledge of
signal processing technology and it's associated programming.
Much research work was necessary to develop the present PACTOR-II
modulation process. Despite all this, it was possible to astonish
visitors with the first prototype PTC-II at the 1994 HAM-Radio