Forums

ADC limitations for bandpass/IF sampling

Started by clam December 13, 2005
Hello Jerry,

> Hands-on matters. Today we have college students and beyond who glibly > compute complex baseband signals on a single twisted pair, and wonder > how to proceed with their simulations. It's east to forget that no > matter how small things become, they're still made up of parts that > interact. >
I had several cases where they could not understand my module specs. And my prose is quite ok since even (older) mechanical engineers never have problems with that. Some of the new grads can't even solder. It's pathetic.
> Acquaintances and neighbors were aghast that I let my kids use tools > like saws and chisels before first grade. I explained that I was careful > to teach them how to use such tools -- in general and specifically -- > without hurting themselves. I too drew a line. I allowed them to use > tools that could cut a finger, but not one that could cut a finger off. >
Probably because you were good parents and your kids paid attention to what you taught them. I remember a trip in the mid west when a big truck pulled up next to us at the market. A little boy hopped out, maybe 14 or 15. "Are you allowed to drive that thing?" "Ahm, well, ahem, pa kinda ruined his back and we really need some stuff for the farm". He had been in front of us for 10 miles or so and all I could say is he drove like a pro, very safely. Regards, Joerg http://www.analogconsultants.com
Hello Al,

> Its wasn't tougher, just different. >
Maybe not tougher but more expensive. Even in 2005 Dollars our allowances were much smaller than today's.
> One of the changes that I think will affect our profession is that it is > very difficult for a kid to get started if he wants to build hardware. >
Nah. Recently I needed some CD4000 chips right away so I drove into town and picked them up at an electronics store. All between 30 and 50 cents a piece. When I grew up you couldn't touch any of these for under $4. Just imagine what that would be in 2005 Dollars. Now you can buy a uC for a couple Dollars and program it for free by just making a serial cable and hooking up a little level translation. Back then any kind of processor cost more than a decent bicycle and wouldn't work without external RAM. I paid more than $25 for one lone memory chip which offered a whopping 1k (kilobits, not kilobytes). I'd really needed 2k but that was way out of reach. Oh, and I had to punch in the data with buttons until blisters showed up. The only computer was at my fathers work, a huge IBM mainframe. When I built a small frequency counter I had to wait a few weeks before its sensitivity could become better than 1Vpp. That's because an AF126 was almost $10 at the local radio repair store. Too much. So when the snow and ice became manageable I did a (rather scary) bicycle tour of about 20 miles because the store in town had it for under $5. That AF126 had to be treated like a princess on the pea so as not to fry it, ever. I mounted it in a socket so it could be used in another circuit while I didn't need to run the counter. Nowadays you can get a whole bag of similar speed BJTs for a Dollar or two. Regards, Joerg http://www.analogconsultants.com
Richard Owlett <rowlett@atlascomm.net> wrote in
news:11q665ofjhmcfb4@corp.supernews.com: 

> Al Clark wrote: > [*SNIP*] >>>>Engineering is the art of making what you want from things you can >>>>get. < >>> >>>That's why engineering was more fun in the old days. It was tougher. >> >> >> Its wasn't tougher, just different. >> >> One of the changes that I think will affect our profession is that it >> is very difficult for a kid to get started if he wants to build >> hardware. >> >> You probably need several thousand dollars of used equipment to start >> (microscope, good soldering iron, etc.) This is a lot of money for a >> 16 year old kid. >> >> Of course, we didn't have personal computers..... >> > > *WHAT* ? > > just how do you justify that monetary outlay?
Microscope with Boom & Light: $500-$1000 Soldering Station $150 Oscilloscope $250-$750 Handtools $50-$250 Signal Generator, Multimeter, etc. Solder, Flux, Antistat Mat, etc... This is before buying parts. Sure, you can still buy thru hole parts for many things, but I think you will find that you cannot avoid SMT parts for very long. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
Al Clark <dsp@danvillesignal.com> writes:

> I still call powering up a circuit the first time, the smoke test. > > Its been a long time since one actually smoked (they don't always work, > but they tend to be a lot more benign).
When I was tutoring 1st year engineering labs, by far the biggest mistake students had made when they said "it doesn't work" was to leave the power supply off. I _know_ it's bad, but I used to shout <BANG> when they turned the power supply on. :-) And nine times out of ten, everything worked. There were just two times I remember anything "letting the smoke out". Once it was an electrolytic capacitor that went <BANG> and the other time the students got some diodes to glow faintly red... and they we'ren't SUPPOSED to be LEDs. Ciao, Peter K.

Peter K. wrote:


> When I was tutoring 1st year engineering labs, by far the biggest > mistake students had made when they said "it doesn't work" was to > leave the power supply off. > > I _know_ it's bad, but I used to shout <BANG> when they turned the > power supply on. :-) >
The engineers who work on the power electronics are usually very good engineers. Many of them are stutterers also. Perhaps the folks who were not that good just didn't survive. VLV
Peter K. wrote:
> Al Clark <dsp@danvillesignal.com> writes: > > >>I still call powering up a circuit the first time, the smoke test. >> >>Its been a long time since one actually smoked (they don't always work, >>but they tend to be a lot more benign). > > > When I was tutoring 1st year engineering labs, by far the biggest > mistake students had made when they said "it doesn't work" was to > leave the power supply off.
When I was doing audio service, a fellow brought me a newly wired Heathkit power amplifier to fix. When I asked him what the problem was, he said, "I don't know. I didn't have the guts to turn it on." Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Steve Underwood wrote:
> When I was 12, my father let me build valve/tube equipment running on > 400V to 500V. He was an electro-mechanical engineer, so he fully > understood what he was letting me do. There is *absolutely* *no* *way* > my two kids are going to do that when they are 12 :-)
I attended a talk given my Gorden Moore recently. When asked how he got interested in chemistry, he talked about using the stuff in his chemistry set to blow things up. When asked later about the declining interest in science education in the US, he lamented that maybe it's because you can't get the fun chemistry sets any longer. IMHO. YMMV. -- rhn A.T nicholson d.O.t C-o-M
Hello Peter,

> I _know_ it's bad, but I used to shout <BANG> when they turned the > power supply on. :-) >
My first boss used to walk around, look over your shoulder, reach onto the board, touch a chip or an electrolytic, quickly retract his hand and say "ouch, why does this get hot?" (None of this ever got hot, usually...) Regards, Joerg http://www.analogconsultants.com
Hello Al,

> Microscope with Boom & Light: $500-$1000
How 'bout #3 magnifier glasses (a buck at the Dollar Store) and a loupe on the swivel arm of a discarded drafting table lamp (pretty much free)? Regards, Joerg http://www.analogconsultants.com
Vladimir Vassilevsky wrote:

> > > Peter K. wrote: > > >> When I was tutoring 1st year engineering labs, by far the biggest >> mistake students had made when they said "it doesn't work" was to >> leave the power supply off. >> >> I _know_ it's bad, but I used to shout <BANG> when they turned the >> power supply on. :-) >> > > The engineers who work on the power electronics are usually very good > engineers. Many of them are stutterers also. Perhaps the folks who were > not that good just didn't survive. > > VLV >
-- and the folks who aren't that nervous? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com