Ray The Microwave SDR project was set up to address this specific requirement :-
uwsdr.net The aim of the project is to provide SDR solutions covering the bands 50MHz to 24GHz. How is this done? Well, first some background info :- There are two main types of SDR in use today for the HF bands; direct conversion and direct sampling. Briefly - direct conversion uses a Local Oscillator operating at the wanted frequency to convert an incoming Rx signal down to baseband, where two quadrature signals I and Q are generated. These are then sampled and converted to digial for processing, usually by a PC. This is how the Flex radios and the Softrocks work, to name but two. The bandwidth is limited by the sampling rate, for example 48kHz or 192kHz. Direct Sampling is where the input Rx signal is passed straight into a fast A-D converter. The bandwidth is huge, and now typically covers the whole HF band and beyond. The Perseus HPSDR Mercury and are such receivers - there are lots of others. The uWSDR approach usses direct conversion from the band of interest straight down to basesband in one go; no inttermediate stage required. We then generate I and Q signals and sample at 96kHz with a very high performance A-D converter, the resulting signals then being processed by a PC, simialr to the Flex/Softrock etc. No transverter required, just a PC. The whole thing mounts at the masthead and is connected to the PC by cheap Ethernet cable; the uWSDR has an IP address - no USB or Firewire. And it's not just a receiver, it's a transmitter as well, making a complete VHF/microwave transceiver covering the whole of one band. So the 13cms version will cover the range 2300-2450MHz with no gaps, a bandwidth of 96kHz and a tuning step of 5Hz using a high performance synthesiser. Or at least it will do, when it's finished. The first product is a 2.3GHz transmitter called GeMMA (Generator for Multiple Microwave Applications); protoypes are being tested at the moment but progress is slow. Once GeMMA is sorted the full 2.3GHz transceiver will be done; the paper design exists already, it's just a case of finding the time to work on it! It's an open-source desgin, so anybody will be able to take the hardware and software designs and more or less do what they want with them. The GUI software has been available for some time and has been used with a softrock to make QSOs on 7MHz. Once the hardware is ready it will work at 2.3GHz. Estimated cost is GBP200/EURO200/USD300 for a single-band 100mW transceiver, but as it's open source anybody can make it and sell it at will. I could go on, but more details are available from the project website (above) and there is a Yahoo group for discussion - http://groups.yahoo.com/group/uwsdr/ No, you can't buy it - yet, but we are working hard on solving some technical issues and would appreciate input from anybody interested. regards Grant Hodgson G8UBN OBO the Microwave SDR team > > 1a. new Posted by: "BBS" [email protected] pdq143 Tue Apr 27, 2010 > 8:25 am (PDT) > > Hi I am a returning amateur and now trying to get my head round SDR. > I think this subject is the most interesting but I have a few > questions if anyone is in the mood to help. I am very interested in > VHF &UHF & even SHF. Is there anything equipment wise so far that > works well at those frequencies or am I a bit soon? Does the > hardware have to cost a fortune? Thanks Ray >
