Software Defined Radio (SDR)
Software Defined Radio (SDR) has become one of the most talked about and perhaps most misunderstood technologies to be adopted by amateur radio enthusiasts since the introduction of single sideband back in the 1940s. In many respects, SDR is just a natural progression from the I.F. DSP (intermediate frequency digital signal processing) stages that have been incorporated into amateur radio HF transceivers since the late 1970s. But SDR also encompasses a wide range of small receivers and transmitters that can cover a huge section of the radio spectrum, often capable of receiving signals up to 1.5 GHz and sometimes as high as 10 GHz. This has opened access to the VHF, UHF and microwave bands at a relatively low cost. Where previously you were committed to buying or building narrowband receiver converters or transverters, you can now receive any frequency in the range. However, you should still use an LNA (low noise preamplifier), or a LNB (low noise block converter), mounted at the antenna end of the feeder cable, for microwave frequencies, because it is important to keep the overall receive noise figure as low as possible.
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