Al Clark wrote:> Joerg <notthisjoergsch@removethispacbell.net> wrote in news:Be2Pf.19621 > $rL5.5958@newssvr27.news.prodigy.net: > > >>Hello Randy, >> >> >> >>>>[...] >>>>I still remember the days when I didn't need a microscope >>> >>>Amen, brother. Remember Heathkit? Too bad the miniturization >>>of electronics has made this sort of hobby obsolete. >> >> >>It's really the lack of interest of today's kids in true creativity > > that > >>has caused Heathkit to go down, and the hobby along with it. >> >>Regards, Joerg >> >>http://www.analogconsultants.com > > > I don't think that kids are so different. > > Some of my earliest projects used tubes that usually lit up and then > smoked. > > Later I discovered transistors and I remember scoring an early 4000 CMOS > book (or maybe it was 7400?) > > Today's kids might be building web sites or writing Visual C programs. > Tools and ingredients change over time. The drive for some people to > create something or build something is still much the same. > > There's not an easy path today for a kid to start building hardware. It > takes quite a bit of money for basic tools, etc. The computer is already > at home and available. > > If you want to help create a next generation hardware engineer, find the > right kid and offer to help him (or her) to get started. The kids are out > there.The soldering iron that I built my first circuits with was a lump of copper on the end of an iron rod with a wooden handle. If I let it overheat in the Bunsen burner, I had to re-tin it on the sal amoniac block. The soldering iron I use today was a bargain at $40 20 years ago, and a replacement would be over $100. The cost of buy-in is high. I gave my old Heathkit scope to a high-school freshman some years back. Today he's an EE. I might have helped. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Approach to demodulating AM-signals?
Started by ●March 3, 2006
Reply by ●March 6, 20062006-03-06
Reply by ●March 6, 20062006-03-06
Joerg wrote:> Hello Jerry, > >> >> A surface mount diode and two caps; one to AC couple, the other to >> integrate -- is not a large assemblage of parts. >> > > Might need a resistor as well. Oops, that would be another 1.5 Cents. > > If precision, large dynamic range and linearity are a concern the > reversed transistor might be an option.The trouble with diode and cap is diagonal distortion at high modulation ratios. Full-wave rectification reduces the severity by half, and DC bias can eliminate it. Either way, the circuit isn't quite so simple any more, but it's still a good choice. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●March 6, 20062006-03-06
Al Clark <dsp@danvillesignal.com> writes:> [...] > Later I discovered transistors and I remember scoring an early 4000 CMOS > book (or maybe it was 7400?)Hey Al, remember the old "TI TTL DATABOOK" with all the 74xx parts in it? You were really quite the engineer if you had one of those babies on your bookshelf. My how times have changed! -- % Randy Yates % "Midnight, on the water... %% Fuquay-Varina, NC % I saw... the ocean's daughter." %%% 919-577-9882 % 'Can't Get It Out Of My Head' %%%% <yates@ieee.org> % *El Dorado*, Electric Light Orchestra http://home.earthlink.net/~yatescr
Reply by ●March 7, 20062006-03-07
Randy Yates <yates@ieee.org> wrote in news:m3acc3ufqb.fsf@ieee.org:> Al Clark <dsp@danvillesignal.com> writes: >> [...] >> Later I discovered transistors and I remember scoring an early 4000 >> CMOS book (or maybe it was 7400?) > > Hey Al, remember the old "TI TTL DATABOOK" with all the 74xx parts in > it? You were really quite the engineer if you had one of those babies > on your bookshelf. My how times have changed!I'm not sure which logic book was my first anymore. It seems to me it had a grey cover. Maybe RCA for the 4000 book? I "started" a company while I was in high school just so I could call up the distributors to get a free databook. I would get "We haven't heard of your company before" and I would reply: I'm sure you will soon. They sent me the manuals. I think the books I later coveted the most were my set of Motorola transistor manuals. I built a lot of amplifiers and analog filters in my 20s. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
Reply by ●March 7, 20062006-03-07
Hello Jerry,> > The trouble with diode and cap is diagonal distortion at high modulation > ratios. Full-wave rectification reduces the severity by half, and DC > bias can eliminate it. Either way, the circuit isn't quite so simple any > more, but it's still a good choice. >The use of a transistor "in reverse" might sound a bit unorthodox but it can greatly help here: http://www.edn.com/contents/images/60701di.pdf Regards, Joerg http://www.analogconsultants.com
Reply by ●March 7, 20062006-03-07
Hello Al,> > I don't think that kids are so different. >I think they are different. But it is at least in part to blame on their parents and certainly on our schools. Most of all, I believe parents should not blindly assume "Oh, the school is taking care of education and motivation".> > There's not an easy path today for a kid to start building hardware. It > takes quite a bit of money for basic tools, etc. The computer is already > at home and available. >Nah. I had to plunk down over $2 for a re-labeled SN7400 which might or might not live up to what my hard-to-read xerox of a xerox of someone's data book said. In 1970's Dollars. This was pretty much the whole weekly allowance. Nowadays kids can go to the electronics store in town and buy a dozen CMOS chips for that and their allowance still affords them all the ice cream they want. With us it was either ice cream of transistor, not both. Just imagine: Today you can buy a complete MSP430F2013 development system for twenty bucks. Plugs right into the USB port and you are in business. When I was in need on a 1kb (kilo-bits!) memory I had to save really hard until, finally, the day came when I plunked down all that dough and carried that precious chip home on my bicycle. On the way back I was hoping that my bare-skinned rear tire would hold up just that one more week because I didn't have money left to buy a new one and it had to survice the 5 mile trip to school another three days. Of course, now I still had to save for all the other logic chips I needed to make to do what I wanted it for. Or scrap them out of old IBM mainframe boards.> If you want to help create a next generation hardware engineer, find the > right kid and offer to help him (or her) to get started. The kids are out > there. >They are out there but it's not that many. I try my best to keep them interested. But let's be honest, what do we tell them about their job prospects versus the kids who want to become dentists, physicians or lawyers? Regards, Joerg http://www.analogconsultants.com
Reply by ●March 7, 20062006-03-07
Joerg <notthisjoergsch@removethispacbell.net> wrote in news:Y1mPf.20711$rL5.2623@newssvr27.news.prodigy.net:> Hello Al, > >> >> I don't think that kids are so different. >> > > I think they are different. But it is at least in part to blame on > their parents and certainly on our schools. Most of all, I believe > parents should not blindly assume "Oh, the school is taking care of > education and motivation".Mentors can come from anywhere, parents, teachers, neighbors, etc. On the other hand, I don't think you can teach motivation, ambition, and a certain amount of natural smarts and creativity. I think these attributes are in a portion of every generation. The best engineers have a bit of all these characteristics. Most people don't.> >> >> There's not an easy path today for a kid to start building hardware. >> It takes quite a bit of money for basic tools, etc. The computer is >> already at home and available. >> > > Nah. I had to plunk down over $2 for a re-labeled SN7400 which might > or might not live up to what my hard-to-read xerox of a xerox of > someone's data book said. In 1970's Dollars. This was pretty much the > whole weekly allowance. Nowadays kids can go to the electronics store > in town and buy a dozen CMOS chips for that and their allowance still > affords them all the ice cream they want. With us it was either ice > cream of transistor, not both.And I had to walk 5 miles to school in -30 degree blizzards - both ways uphill..........> > Just imagine: Today you can buy a complete MSP430F2013 development > system for twenty bucks. Plugs right into the USB port and you are in > business. When I was in need on a 1kb (kilo-bits!) memory I had to > save really hard until, finally, the day came when I plunked down all > that dough and carried that precious chip home on my bicycle. On the > way back I was hoping that my bare-skinned rear tire would hold up > just that one more week because I didn't have money left to buy a new > one and it had to survice the 5 mile trip to school another three > days. Of course, now I still had to save for all the other logic chips > I needed to make to do what I wanted it for. Or scrap them out of old > IBM mainframe boards.Buying a dev board is great but it's not going to teach you how to design a circuit, build it, and get it though the "smoke" test. I had to work to buy parts as well. Personal computers still cost more in real dollars than my first soldering iron.> > >> If you want to help create a next generation hardware engineer, find >> the right kid and offer to help him (or her) to get started. The kids >> are out there. >> > > They are out there but it's not that many. I try my best to keep them > interested. But let's be honest, what do we tell them about their job > prospects versus the kids who want to become dentists, physicians or > lawyers?Engineers may on the average make less money than these professions, but by and large we don't starve. This doesn't count the techies who run companies either. There have never been that many of us. My high school class had 550 graduates. I am the only EE, and one of two engineers. I went to a fairly well respected secondary school system (once ranked in the top 20 - US). I do think the media does a horrible job of stereotyping techies in general. We are not all nerds and geeks. I have never worn a calculator on my belt, When I was single, I got dates. I can even hold an intelligent conversation without talking about techie stuff. In this regard, I am not unique. We would probably (at least in the US) attract more young people (especially women) if our society placed a higher social value on engineers and scientists. It's OK if the pretty girl is smart.> > Regards, Joerg > > http://www.analogconsultants.com >-- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
Reply by ●March 7, 20062006-03-07
Hello Al,> > Mentors can come from anywhere, parents, teachers, neighbors, etc. > > On the other hand, I don't think you can teach motivation, ambition, and > a certain amount of natural smarts and creativity. ...I strongly believe you can. If it wasn't for my grandfather who taught me that just about anything can be repaired or built I am not sure I would have studied engineering. He was a steam locomotive engineer and did the long haul routes. When something broke they had to make a new part right there on the locomotive or they'd be stuck for a really long time. So, he tried to pass that skill on to me and others.> > Buying a dev board is great but it's not going to teach you how to design > a circuit, build it, and get it though the "smoke" test. ...Oh, these actually do. For those $20 you get a uC with a 16bit ADC on board. Plus digital ports. Then there are a dozen solder pads where you can connect stuff to your hearts desire, the sky is the limit. You can detach the tiny MSP430 pod from the USB stick and use it in whatever you like. Man, if I had one of those puppies when I built model train sets I would have danced for joy. Back then my "programmable PWM controller" around an astable was controlled but a bunch of resistors and a motor-driven rotary switch scavenged from an old washing machine. Since it was from a really old machine it would occasionally get stuck and then a train would crash. Later I inherited an 8086 from my father's IBM PC because the math coprocessor upgrade contained a new one of these. Oh, what a joy.> ... I had to work to > buy parts as well. Personal computers still cost more in real dollars > than my first soldering iron. >Not really. You can often buy an older machine for $20 at a yard sale. Sometimes they'll give it to you for free just to get rid of it. When neighbors wanted to sell theirs they didn't find any takers even after they placed a sign "free to a good home". Lots of teenage kids passed by. Pentium, lots of RAM, huge HD, all the bells and whistles and the Dell brand. How could they not bite? Guess the tunes from their iPods were drowning out their thoughts. I am writing this on a PC that's almost 10 years old and works just fine. A bit loud in the fan bearings by now but it's great for CAD work since I got a 21" monitor for it. My first solder iron cost about $10. It was a rather dangerous concoction without a PE connection. A decent solder station was way out of reach back then. Even today they run about $500 and you can get a brand new laptop for that.> There have never been that many of us. My high school class had 550 > graduates. I am the only EE, and one of two engineers. I went to a fairly > well respected secondary school system (once ranked in the top 20 - US). >Ours had about 500 who started EE per year. But over 80% of them failed and had to drop out over the years so only a fraction ever made it to MSEE. Maxwell's equations did most of them in.> I do think the media does a horrible job of stereotyping techies in > general. We are not all nerds and geeks. I have never worn a calculator > on my belt, When I was single, I got dates. I can even hold an > intelligent conversation without talking about techie stuff. In this > regard, I am not unique. >Agree. Same here. There is a time when to talk shop and there are times when not to. Else my wife who is a marketeer would have never married me ;-) Regards, Joerg http://www.analogconsultants.com
Reply by ●March 8, 20062006-03-08
Joerg wrote:> Hello Jerry, > >> >> The trouble with diode and cap is diagonal distortion at high >> modulation ratios. Full-wave rectification reduces the severity by >> half, and DC bias can eliminate it. Either way, the circuit isn't >> quite so simple any more, but it's still a good choice. >> > > The use of a transistor "in reverse" might sound a bit unorthodox but it > can greatly help here: > http://www.edn.com/contents/images/60701di.pdf > > Regards, Joerg > > http://www.analogconsultants.comDiagonal clipping in a detector isn't influenced by diode offset. It was a problem with tube circuits too. The integrating cap is charged through the diode when the envelope rises, and discharges through a resistor when the envelope falls. At high audio frequencies and high percentage modulation, the dv/dt called for by the modulation is higher than the RC decay allows, so the falling edge of the audio is replaced by an exponential decay that appears to be a diagonal line. Full-wave operation mitigates the problem by allowing a capacitor half as large. Returning the bleeder resistor to a sufficiently large negative bias eliminates the problem. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●March 8, 20062006-03-08
On Tue, 07 Mar 2006 02:53:32 GMT, Randy Yates <yates@ieee.org> wrote:>Al Clark <dsp@danvillesignal.com> writes: >> [...] >> Later I discovered transistors and I remember scoring an early 4000 CMOS >> book (or maybe it was 7400?) > >Hey Al, remember the old "TI TTL DATABOOK" with all the 74xx parts in >it? You were really quite the engineer if you had one of those babies >on your bookshelf. My how times have changed! >-- >% Randy Yates % "Midnight, on the water...Hi, That was what we called the "Orange" book, for the color of the cover. We used that book so much that we began to memorize the actual pin numbers of the internal gates, such as the "quad two-input Nand" 7400. Gosh, I had a copy of that book, but I can't find it. Too bad. Although I still have my RCA vacuum tube data book. (Jerry probably remembers that guy.) It has a red cover and 500 pages of pin numbers and performance curves, all for $1.25 !! [-Rick-]
