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This project started in the middle of 2003, when i read some articles about DRM (Digital radio mondiale) and found the website of Christoph Petermann (DF9CY), where he published some schematics for a DRM demonstration receiver.
Because of my interests as radio amateur and engineer, i decided to build my own microcontrolled direct conversion receiver with a DDS-VFO. The first version of this receiver (downmixing the RF to a 12kHz IF) includes the microcontroler (with LCD, rotary encoder and keypad), the DDS-unit, the mixer stage and the 12kHz-amplifier. The software for the MCU was very simple with a fix table of DRM station frequencies. It works fine for a first attempt, but there was a lot room for improvements...
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Fig. 1: View of the DDS-VFO
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In autum 2003 i came in contact with Burkhard Kainka (DK7JD), who did a lot of cuircuits for DRM reception, and we had alive exchange of ideas (many thanks to him for his support, he is a really great author and engineer).
Some months and discarded concepts later, i decided to separate the DDS-VFO and the DRM receiver, on the one hand to have a new nice and useful gadget in my ham shack (the VFO) and on the other hand to be more flexible with the DRM receiver. In this configuration i can test some further receiver concepts without roasting around the DDS, just plugging a new frontend. The result is shown in fig.1. Also the µC-firmware grew up and i added a lot of features described in Operation.
The DDS-VFO/DRM-RX are not comercial products, but an amateur project and therefore provided "as is". This website is intended to be a proposal for hams and other amateurs. So all the schematics, layouts and the firmware sourcode can be downloaded and applied for free, as long as it´s for a non-comercial project. If there are questions, don´t be afraid to ask...
(Some of the pages aren´t ready for upload yet. They will be added as soon as possible...)
vy 73, Thorsten DL9SEC ( www.dl9sec.de)
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