On 8/30/11 6:12 PM, Rick Lyons wrote:> > Hi Robert, > you are correct in that the 'impulse invariance' filter > design technique (where the discrete-time filter's impulse > response is a sampled version of a continuous-time filter's > impulse response) is in almost every DSP textbook in existence.i mean, what else can "impulse invariant" mean? some technique that *doesn't* preserve the impulse response? sheesh.> The earliest description of that filter design technique > that I've found is in a paper by two of DSP's greatest > pioneers: "Digital Filter Design Techniques in the Frequency > Domain", by Charles rader and Bernard Gold. That paper was > in the Feb. 1967 issue the the 'Proceedings of the IEEE'. > That filter design technique, then, is over 40 years old.well, it was (along with bilinear, and emulating Euler's forward method of diff eq.) taught to me about 30 or 35 years ago.> Robert, where were you in 1967? Ha ha. > That year I was enrolled in a two-year technical school > tryin' to figure out how vacuum tubes, capacitors, and > transformers worked.oh, at that time i was a 6th or 7th grader, picking my nose in a small, boring, and nondescript town in North Dakota reasonably close to Fargo. i was, at that time a ham operator (WB0CCA) and any gear that a kid like me could buy was tube oriented (the VFO in my Heathkit HW-100 had a one or two transistors in it). before that i had an older rig that i started out with that had a cathode-keyed CW transmitter. then i started to look into how tubes worked. i sorta understood, qualitatively, the concept on how the negatively-biased grid could control the flow of electrons from the cathode to the plate. but everything else i learned then was simple rote learning (enough to pass the Conditional class ham radio license test). didn't know any Laplace or Z transforms until ca. 1975. in fact, i didn't really figger anything out for real until i was in college. i gotta get something done for FEMA. L8r, guyz. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
obtaining discrete time model from impulse response or transfer function
Started by ●August 28, 2011
Reply by ●August 30, 20112011-08-30
Reply by ●August 30, 20112011-08-30
robert bristow-johnson <rbj@audioimagination.com> wrote: (snip)> oh, at that time i was a 6th or 7th grader, picking my nose in a small, > boring, and nondescript town in North Dakota reasonably close to Fargo. > i was, at that time a ham operator (WB0CCA) and any gear that a kid > like me could buy was tube oriented (the VFO in my Heathkit HW-100 had a > one or two transistors in it). before that i had an older rig that i > started out with that had a cathode-keyed CW transmitter. then i > started to look into how tubes worked.I was reading not so long ago about Armstrong and his radio developments. It seems that at the time tubes weren't really understood well at all. Even how to build an oscillator was new at the time, and yet he figured out FM.> i sorta understood, > qualitatively, the concept on how the negatively-biased grid could > control the flow of electrons from the cathode to the plate. but > everything else i learned then was simple rote learning (enough to pass > the Conditional class ham radio license test).Is that the usual way to pass FCC license tests? When I was in 6th and 7th grade, I liked to read Popular Electronics. Some articles, and many cartoons, were about HAM radio and the FCC tests. It is, in any case, interesting how many inventions were made when things weren't really understood well enough yet. The book also had a long description on the Wright brothers ariplane developments. How many mistakes they made along the way. (and models that almost crashed.) -- glen
Reply by ●August 30, 20112011-08-30
On 8/30/11 8:44 PM, glen herrmannsfeldt wrote:> robert bristow-johnson <rbj@audioimagination.com> wrote: >...> >> i sorta understood, >> qualitatively, the concept on how the negatively-biased grid could >> control the flow of electrons from the cathode to the plate. but >> everything else i learned then was simple rote learning (enough to pass >> the Conditional class ham radio license test). > > Is that the usual way to pass FCC license tests?well, this 7th grader was not going to answer a technical question about some circuit by writing node-voltage equations with phasor quantities and solve an equation with real and imaginary quantities. most of the questions were about radio concepts (AF, RF, modulation, dipole antenna) and about the FCC rules. and even though i passed (the other half of the test was a 13 WPM morse code test) i'm sure i didn't get every question correct. some of the technical questions i may have gotten right because i recognized something and guessed well on a multiple choice.> When I was in 6th > and 7th grade, I liked to read Popular Electronics. Some articles, > and many cartoons, were about HAM radio and the FCC tests.i liked PE also. at the time, chips and even PC boards were novel. there was no LSI then. the hot items were "multi-vibrators". the other books i remember reading were from ARRL (the Amateur Radio Handbook). i also got QST magazine, and later got a mag called "Ham Radio". (there was another one i didn't get, i think it was called "73".) eventually i moved "up" to the HW-100 and SSB. i remember lusting after a product called the Signal One CX-7. i can't remember much else from those daze. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●September 2, 20112011-09-02
On 8/30/2011 6:36 PM, robert bristow-johnson wrote: ...> i gotta get something done for FEMA. L8r, guyz.FEMA? Champlain just spiked up 2 inches, but it's still six inches below its recent nearly disastrous high. Jerry -- Engineering is the art of making what you want from things you can get.
Reply by ●September 2, 20112011-09-02
On 9/1/11 11:24 PM, Jerry Avins wrote:> On 8/30/2011 6:36 PM, robert bristow-johnson wrote: > > ... > >> i gotta get something done for FEMA. L8r, guyz. > > FEMA? Champlain just spiked up 2 inches, but it's still six inches below > its recent nearly disastrous high. >uh, it's *feet*. it just shot up 2 feet (now it's leveled off) and it's nearly 6 feet less than the crest last May and more than 2 feet below flood stage. but i am still dealing with FEMA paperwork (because i'm still doing repairs/remodeling). you see, guys, i'm one of them freeloaders getting money i didn't earn from the guvmint. (now FEMA reserves are down to $800 million, they are now diverting long-term funding to short-term, because of Irene and also because of the likes of Eric Cantor.) BTW, the flow of the river from this last incident (Irene) has chewed up about a 6 foot by 40 foot piece of river bank very close to where i live. lot'sa serious erosion. maybe in a couple of decades the river will be flowing through my house and not just during flooding as it did last spring, but permanently. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●September 2, 20112011-09-02
On Fri, 02 Sep 2011 00:11:21 -0400, robert bristow-johnson wrote:> On 9/1/11 11:24 PM, Jerry Avins wrote: >> On 8/30/2011 6:36 PM, robert bristow-johnson wrote: >> >> ... >> >>> i gotta get something done for FEMA. L8r, guyz. >> >> FEMA? Champlain just spiked up 2 inches, but it's still six inches >> below its recent nearly disastrous high. >> >> > uh, it's *feet*. > > it just shot up 2 feet (now it's leveled off) and it's nearly 6 feet > less than the crest last May and more than 2 feet below flood stage. > > but i am still dealing with FEMA paperwork (because i'm still doing > repairs/remodeling). you see, guys, i'm one of them freeloaders getting > money i didn't earn from the guvmint. (now FEMA reserves are down to > $800 million, they are now diverting long-term funding to short-term, > because of Irene and also because of the likes of Eric Cantor.) > > BTW, the flow of the river from this last incident (Irene) has chewed up > about a 6 foot by 40 foot piece of river bank very close to where i > live. lot'sa serious erosion. maybe in a couple of decades the river > will be flowing through my house and not just during flooding as it did > last spring, but permanently.I read your last paragraph and the opening pages of "Sometimes a Great Notion" sprang to mind. -- www.wescottdesign.com
Reply by ●September 2, 20112011-09-02
> On 8/30/11 8:44 PM, glen herrmannsfeldt wrote: >> robert bristow-johnson <rbj@audioimagination.com> wrote: >> > ... >>>> >> Is that the usual way to pass FCC license tests? >There are many reasons to learn the FCC tests' Q&A by rote: 1) You are focusing on the right questions. 2) If some of the "right" answers seem wrong then either you will learn something new or you will learn what that "right" answer needs to be. Don't fight City Hall. And, 3) because there are a lot more questions than there will be on the exam, there really is a chance that you will learn something. and 4) My favorite example are the tables of allowed frequencies and such regulatory stuff. How else than by rote? My mom was kind enough to read the ham radio questions to me when I was a kid so I could practice answering them. She didn't know how to pronounce a few of the words, which was cute. I think she first said: linEER ... for linear. Since I had let my license lapse because I wasn't going to twiddle knobs nights and weekends when I'd spent all day at work doing that stuff, I had to take the exams over again for AC7VR: I walked into the room and told the examiners that I was going to take ALL the test units then and there. That was a surprise. When I took that last unit for Extra class I was pretty confident that it had gone well. But, when it was graded, the result was really, really bad. None of the examiners seemed too surprised but I said: "can't be" because I had only one or two that I wondered about. Someone suggested that the scoring sheet had been rotated .. and sure enough. It seems that the scoring sheets are designed to score 4 tests each. Flip top to bottom and flip front to back. Anyway, I sure did rote learning for those tests even though I could answer many of them off the top of my head or do the calcuations or ... whatever. The issue is passing the test. You better shoot your best shot. I was a Boy Scout too. Motto: "Be Prepared". Seems fitting here. So, yes, I would think that this is the usual way (and advised way) to pass FCC tests. But, indeed, it makes one wonder doesn't it? What if the underlying philosophy (or result) is that you are demonstrating some understanding of technical language, can read, that you've worked at it, can remember, can focus, that the stuff will rub off if you don't know or understand it very well yet, etc? Fred
Reply by ●September 3, 20112011-09-03
On 2 Sep, 21:23, Fred Marshall <fmarshallxremove_th...@acm.org> wrote:> > On 8/30/11 8:44 PM, glen herrmannsfeldt wrote: > >> robert bristow-johnson <r...@audioimagination.com> wrote: > > > ... > > >> Is that the usual way to pass FCC license tests? > > There are many reasons to learn the FCC tests' Q&A by rote:FCC...? Rune
Reply by ●September 3, 20112011-09-03
On 9/3/11 8:46 AM, Rune Allnor wrote:> On 2 Sep, 21:23, Fred Marshall<fmarshallxremove_th...@acm.org> wrote: >>> On 8/30/11 8:44 PM, glen herrmannsfeldt wrote: >>>> robert bristow-johnson<r...@audioimagination.com> wrote: >> >>> ... >> >>>> Is that the usual way to pass FCC license tests? >> >> There are many reasons to learn the FCC tests' Q&A by rote: > > FCC...? >Ferengi Commerce Commission. don't piss those guys off. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●September 3, 20112011-09-03
On 9/3/2011 8:46 AM, Rune Allnor wrote:> On 2 Sep, 21:23, Fred Marshall<fmarshallxremove_th...@acm.org> wrote: >>> On 8/30/11 8:44 PM, glen herrmannsfeldt wrote: >>>> robert bristow-johnson<r...@audioimagination.com> wrote: >> >>> ... >> >>>> Is that the usual way to pass FCC license tests? >> >> There are many reasons to learn the FCC tests' Q&A by rote: > > FCC...?Federal Communications Commission; jurisdiction over matters radio and telephone. Jerry -- When ideas fail, words come in very handy. -- Johann Wolfgang von Goethe
