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#31
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An SDR or DDS question?
Jerry Stuckle wrote:
On 2/9/2016 12:52 AM, Brian Reay wrote: Perfectly normal, at least in the UK, for students studying various courses (certainly the sciences) to study a programming language (in my Uni days Fortran). My wife certainly did, we were married while at Uni (still are of course) and we often spent lunch times preparing 'punch cards' which were the entry method for the Uni Fortran machines. And I suppose you learned about exothermic reactions in a World History class. In the United States, computer languages are taught in Computer Science courses, not Chemistry. Well that's yet another difference. Until the great dumbing-down of university courses in the UK in recent years,[1] first degrees tended not to be modular, and the department of the primary subject arranged lecturers in necessary ancillary subjects as part of the main course. [1] which doesn't apply to all universities. -- Roger Hayter |
#32
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An SDR or DDS question?
Roger Hayter wrote:
Jerry Stuckle wrote: On 2/9/2016 12:52 AM, Brian Reay wrote: Perfectly normal, at least in the UK, for students studying various courses (certainly the sciences) to study a programming language (in my Uni days Fortran). My wife certainly did, we were married while at Uni (still are of course) and we often spent lunch times preparing 'punch cards' which were the entry method for the Uni Fortran machines. And I suppose you learned about exothermic reactions in a World History class. In the United States, computer languages are taught in Computer Science courses, not Chemistry. Well that's yet another difference. Until the great dumbing-down of university courses in the UK in recent years,[1] first degrees tended not to be modular, and the department of the primary subject arranged lecturers in necessary ancillary subjects as part of the main course. [1] which doesn't apply to all universities. A stunningly inaccurate statement. It was possible to take different modules in top rated Universities (from a selected list) to get a degree 40 years ago. Including Oxbridge. It still is. True, you couldn't mix, say, engineering and tourism but different modules in engineering (for example) were perfectly normal. Typically, the first year was fixed but after that you could specialise in, say, digital electronics and computing or electrical engineering and electronics. |
#33
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An SDR or DDS question?
Brian Reay wrote:
Roger Hayter wrote: snip Well that's yet another difference. Until the great dumbing-down of university courses in the UK in recent years,[1] first degrees tended not to be modular, and the department of the primary subject arranged lecturers in necessary ancillary subjects as part of the main course. [1] which doesn't apply to all universities. A stunningly inaccurate statement. It was possible to take different modules in top rated Universities (from a selected list) to get a degree 40 years ago. Including Oxbridge. Things like PPE, or PPP you mean? Whatever the theory, in practice you couldn't dream up your own combination, there were some established ones It still is. True, you couldn't mix, say, engineering and tourism That of course is what I meant. You couldn't do a Keele style degree of knitting, Serbo-Croat, media studies and physics. I wasn't trying to imply that their was no choice of modules in a subject. The point I was making, of course, that things like computer programming for chemists, while taught by the subject experts, was part of the Chemistry degree, not a separately credited module. but different modules in engineering (for example) were perfectly normal. Typically, the first year was fixed but after that you could specialise in, say, digital electronics and computing or electrical engineering and electronics. -- Roger Hayter |
#34
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An SDR or DDS question?
On 09/02/16 20:46, Roger Hayter wrote:
Brian Reay wrote: Roger Hayter wrote: snip Well that's yet another difference. Until the great dumbing-down of university courses in the UK in recent years,[1] first degrees tended not to be modular, and the department of the primary subject arranged lecturers in necessary ancillary subjects as part of the main course. [1] which doesn't apply to all universities. A stunningly inaccurate statement. It was possible to take different modules in top rated Universities (from a selected list) to get a degree 40 years ago. Including Oxbridge. Things like PPE, or PPP you mean? Whatever the theory, in practice you couldn't dream up your own combination, there were some established ones It still is. True, you couldn't mix, say, engineering and tourism That of course is what I meant. You couldn't do a Keele style degree of knitting, Serbo-Croat, media studies and physics. I wasn't trying to imply that their was no choice of modules in a subject. The point I was making, of course, that things like computer programming for chemists, while taught by the subject experts, was part of the Chemistry degree, not a separately credited module. Roger, rather than trying to back pedal, just admit you were posting nonsense. If they were not modules, what were they? Even if they were called 'units', 'blocks', or whatever, it is irrelevant. Even now, there are plenty of degrees which don't allow wild and wonderful combinations of modules. What happened, were you replaced by someone younger and better qualified and it has made you bitter? -- Now we've developed the technology to 'chip' and track every dog, why not extend it to sex offenders. |
#35
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An SDR or DDS question?
Brian Reay wrote:
Roger, rather than trying to back pedal, just admit you were posting nonsense. If they were not modules, what were they? Even if they were called 'units', 'blocks', or whatever, it is irrelevant. Even now, there are plenty of degrees which don't allow wild and wonderful combinations of modules. What happened, were you replaced by someone younger and better qualified and it has made you bitter? In your eagerness to make bizarre rude remarks about me you seem to forget we were both on the same side in the originai discussion, which was when someone expressed surprised about a Fortran course in a Chemistry degree. You seem to have gone off at a tangent somewhere. I must take more care about not replying to you, I suppose! -- Roger Hayter |
#36
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An SDR or DDS question?
Roger Hayter wrote:
. You couldn't do a Keele style degree of knitting, Serbo-Croat, media studies and physics. Damn shame, if you ask me. That degree would make for some really quite interesting, and well-scarved, graduates. -- STC // M0TEY // twitter.com/ukradioamateur |
#37
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An SDR or DDS question?
On 2/9/2016 4:52 PM, Roger Hayter wrote:
Brian Reay wrote: Roger, rather than trying to back pedal, just admit you were posting nonsense. If they were not modules, what were they? Even if they were called 'units', 'blocks', or whatever, it is irrelevant. Even now, there are plenty of degrees which don't allow wild and wonderful combinations of modules. What happened, were you replaced by someone younger and better qualified and it has made you bitter? In your eagerness to make bizarre rude remarks about me you seem to forget we were both on the same side in the originai discussion, which was when someone expressed surprised about a Fortran course in a Chemistry degree. You seem to have gone off at a tangent somewhere. I must take more care about not replying to you, I suppose! The issue was not a FORTRAN course in a Chemistry degree. It was a FORTRAN course provided by the Chemistry department - and that by "professors" who didn't know FORTRAN. But then trolls never learned to read. They just contradict things they know nothing about. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#38
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An SDR or DDS question?
On 2/6/2016 4:49 PM, Michael Black wrote:
On Sat, 6 Feb 2016, Brian Howie wrote: In message ple.org, Michael Black writes On Sat, 6 Feb 2016, gareth wrote: "Brian Howie" wrote in message ... In message , gareth writes Presumably those SDR rigs which do not work on the IF but directly from antennae must have, separately from the DSP processor, some semblance of a DDS generator (but without the final DAC) to act as the equivalent of the VFO, for I cannot perceive that a fractional-Hz tuning rate could be achieved with machine code running in the DSP processor? I'm not an expert ,but I think what you're asking is " how is the local oscillator generated" in a direct conversion SDR and "what determines its resolution" There is an example here, :- http://www.radioelementi.it/public/saqrx.pdf The "c" source code is here,which I can just about understand ( My software background is FORTRAN and Matlab) :- https://sites.google.com/site/sm6lkm/saqrx/ Softies shouldn't have a problem with it although I was able to mess about with it and recompile it successfully In this case the spectrum is dc to 22050Hz in 512 steps. It's not the LO precision ( it's floating point in this one) that limits it but the size of the FFT , the sample rate and thus the record length, that sets the minimum FFT bin width . This one tunes in lumps of about 43Hz Thank-you Brian, but what you have URLed is already at baseband, being VLF. I thought that was the norm, not much doing A/D at signal frequency. Initially, it was too fast for the hardware to handle, but there are probably some good reasons still to downconvert. Michael Correct , but Gareth asked about the software equivalent of a DDS frequency synthesiser or VFO. The "directly from antenna" in his post threw me. If there's a heterodyne conversion, which is what he was asking I see now, then there has to some sort of local oscillator. The way I read it was that he was asking how to tune something that directly converted to digital. Sorry. I'm a bit confused by the many comments about the original post, but there is such a thing as a direct down conversion receiver. As long as the input is sampled fast enough for the signal frequency or at least fast enough for the bandwidth when using sub-sampling and there are adequate filters on the input, this can work. The trouble is the filtering. I believe that is why IF frequencies have been used, to filter the signal more easily. -- Rick |
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