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www.southgatearc.org
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WebSDR receiver on 20m, 40m and 80mThe amateur radio club ETGD at the University of Twente provide a WebSDR HF receiver for use by Radio Amateurs and listeners around the world. In contrast to other web-controlled receivers, this can be tuned by multiple users simultaneously, thanks to the use of Software-Defined Radio. Tuning is done either by clicking or dragging with the mouse on the waterfall display, by typing a frequency into the text box, or by using the up/down buttons. The bandwidth can be changed by clicking the appropriate buttons, and by 'dragging" the edges of the yellow passband indication. The present system consists of the following hardware: • A W3DZZ trap-dipole for the 80 and 40 meter amateur radio bands, on top of the 40 m high "Hogekamp" building of the University of Twente. • Simple bandpass filters for the 80 m, 40 m and 20 m bands. • A quadrature mixer in which the signals are mixed with about 7080.7 kHz. This mixer is a Quadrature Sampling Detector or "Tayloe mixer", the well-known circuit with a four-position CMOS switch, which is also used in many amateur radio SDR front-ends such as the SDR-1000 and the SoftRock. • Similar mixers operating at 3600 kHz and 14161 kHz. • A PC with soundcards to receive and process the signals coming out of the quadrature mixers. The PC is an old Pentium-III at 1 GHz, running Linux and the WebSDR server software (written by PA3FWM). To use the WebSDR HF radio receiver go to PA3FWM's Software Defined Radio page
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