Interesting: I did not recognise the acronym 'SDR', but am aware of the concept of a 'software-controlled radio'. I have made a few comments below, based on my first reading of the article.
I see that an 'external RF unit' is required and that one key feature of this unit is the production of in-phase and quadrature signals so that the image freq. can be eliminated. This is not new. I recall seeing an conventional all-analogue comms. receiver design that used that very technique back in the mid-'70s, primarily intended for naval comms. I've also seen it implemented more recently in UHF & SHF comms. systems. The author makes a disguised recognition that the performance of any SDR radio will be very largely determined by the performance of this 'external unit': he refers to problems of image rejection and problems of strong signal performance (the latter being the usual trouble with semi-conductors: nothing new). I also have a bit of a problem with the author's comment that the "Japanese will have a problem developing SDR since their coding will not be open source, and 'open source' is the 'Amateur way' ". Since when has any manufacturer deemed that compliance with current Amateur philosophies (as opposed to basic functionality) was a necessary pre-requisite for manufacturing a product that will be successful in the Amateur Radio market? In my experience, although Amateurs may have an initial idea, it is soon followed by such manufacturers developing their own implementation of that idea to produce a marketable and mass-produced product and on the grounds of competition protection, any software coding will, consequently, be protected. And if it is so protected, so what? The vast majority of Amateur Radio equipment produced today is way beyond the capabilities of most Amateurs to modify or repair it anyway.
There are quite a few other technical aspects of his article (and some with the presentation style and grammar issues - but I'll overlook those
) that I have problems with, but what I have commented on, as above, will do for now - pending any other comments by others arising about this Thread and its sited reference within it.
Al.
I see that an 'external RF unit' is required and that one key feature of this unit is the production of in-phase and quadrature signals so that the image freq. can be eliminated. This is not new. I recall seeing an conventional all-analogue comms. receiver design that used that very technique back in the mid-'70s, primarily intended for naval comms. I've also seen it implemented more recently in UHF & SHF comms. systems. The author makes a disguised recognition that the performance of any SDR radio will be very largely determined by the performance of this 'external unit': he refers to problems of image rejection and problems of strong signal performance (the latter being the usual trouble with semi-conductors: nothing new). I also have a bit of a problem with the author's comment that the "Japanese will have a problem developing SDR since their coding will not be open source, and 'open source' is the 'Amateur way' ". Since when has any manufacturer deemed that compliance with current Amateur philosophies (as opposed to basic functionality) was a necessary pre-requisite for manufacturing a product that will be successful in the Amateur Radio market? In my experience, although Amateurs may have an initial idea, it is soon followed by such manufacturers developing their own implementation of that idea to produce a marketable and mass-produced product and on the grounds of competition protection, any software coding will, consequently, be protected. And if it is so protected, so what? The vast majority of Amateur Radio equipment produced today is way beyond the capabilities of most Amateurs to modify or repair it anyway.
There are quite a few other technical aspects of his article (and some with the presentation style and grammar issues - but I'll overlook those
) that I have problems with, but what I have commented on, as above, will do for now - pending any other comments by others arising about this Thread and its sited reference within it.Al.
