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WiNRADiO G39DDC User’s Guide
108
Appendix A – SDR and DDC Primer
This note is intended to help “traditional” radio enthusiasts understand the
technology differences between old style analog receivers and the new
generation of Software Defined Radio (SDR), especially with reference to the
WiNRADiO Excelsior.
Analog Receivers
Prior to the era of computer-interfaced radio receivers, a block diagram of a
typical HF receiver would look similar to that below. Incoming radio signals are
down-converted via one or more conversion processes, all using analog
components, tuned circuits, and various amplifiers, mixers and oscillators.
Following the final down-conversion, the resulting signal is applied to a
demodulator, and then to the audio output circuits:
These receivers depend only on hardware for their performance and
functionality. In the currently prevailing nomenclature of the SDR industry, they
are formally referred to as SDR Tier Zero receivers, meaning that there is no
involvement of software at all.
First Generation SDR
With the proliferation of personal computers into every aspect of our life, some
manufacturers realized that the world of radio had essentially remained
unaffected by computers and the radio receivers of the day would benefit from
some degree of computerization. WiNRADiO led that movement with the
introduction of the world’s first consumer PC-based communications receiver
in 1995, the award-winning WR-1000i model – a fully-fledged general-
coverage receiver on a PC card. A serial-interfaced (RS-232) external model