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I don't much like the receivers I've used in contemporary tranceivers -- the general coverage synthisized open front end ones. (I hasten to add I haven't used any of the $4000 rigs; can't afford them). But the ones I have used seem plagued with near-signal desensitization, front end overload, etc., and I suppose all that comes from putting the selectivity so far downstream. I'm almost tempted to get an old 75s4 and shut up, but I really don't need another room heater, so, instead, I'm thinking of building my own receiver along the lines laid down by the late Doug DeMaw in his _QRP Notebook_. Single conversion 160m superhet with Collins mechanical filters in the IF and a series of down-converters for the other bands. Anybody got any experience with the DeMaw Design? Jim, K5YUT There was a project to design a REALLY good sigle conversion ham radio and here is the website: http://www.warc.org.uk/cdg2000/The%2...ransceiver.htm It was designed to have a fantastic dynamic range and, after seeing some of the schematics, it has quite a few good ideas. The mixers and crystal filters are worth studying. One of the designers made a helical coil VCO with really good phase noise, although the mechanical details were complex. These days, I'd want to look into the AD9954 DDS design. Probably still have to do something about DDS spurs, but they are fairly low as is. ================== So, it seems to me that there are a lot of designs for homebrew gear. You need to look at your specific requirements to see what will suit you. In my case, I live in a very RF HOT location, with quite a few powerful signals. I might take the extra effort to go for maximum dynamic range. Probably ovekill for most ham locations, but necessary for me. Jim N6BIU -- 15:10 Pacific Time Zone Dec 26 2006 International Time 23:10 UTC 26.12.2006 |
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