EE rant

Oh, but the people I worked with were NOT careful. One coworker rewrote a function from the main library, but didn't give his variant a different name. Big oops if you didn't know exactly what order to offer the libraries to the linker. Another coworker decided his filenames would never exceed 72 characters, and when (disk/directory/subdirectory/name combined) added up to 73 characters for a particular subdirectory, programs that worked inputting from user9 directory failed for user10 directory.

Neither coworker was open to change.

I've been thinking for some time now that EE schools don't turn out

Yeah, both schools were great placees to study, 40 years ago.

They're orthogonal in cylindrical coordinates, i.e. weighted by a factor r. They also have analogues to Fourier series, e.g. the azimuthally-symmetric radial modes of a circular-cylinder metal waveguide all have J_0 dependence, but they're orthogonal because the overlap integral

integral (0. 1) J_0(r/a) * J_0(r/b) r dr

where a and b are zeros of J_0 gives 0 when a != b.

Bessel functions have a lot of pretty math associated with them, and so do a lot of other 'special functions', like Martin's prolate spheroidal wave functions that turn out to be amazing windows. In my thesis, I needed Struve functions, which are the Mellin transforms of Bessel functions. My case was the 1-D integral of a 2-D Airy pattern,

h(r) = J_1(k r)/( k r)

associated with scanning a diffraction spot across a sample in 1-D. (I was pretty proud of the result until I found out it had been published by Lord Rayleigh, as I mentioned awhile back.)

Abramowitz & Stegun has all sorts of cool-sounding stuff like confluent hypergeometric functions, but I don't know any more about them.

Zernikes are quite different from stuff like waveguide modes. They form a family of polynomials that are orthonormal on the unit disc, and are most commonly used to represent phase deviations due to optical aberrations.

I've never managed to find a use for them, despite trying. To my eye their nice properties are mostly illusory. From a sci.optics post of mine from long ago,

[**] Seidels are polynomial coefficients in cylindrical coordinates. Well known ones are defocus, astigmatism, coma, and primary spherical aberration.

Cheers

Phil Hobbs

Some people will always be sloppy. Don't do that.

We assume that ICs and inductors and connectors and whatever are factory tested before we buy them; we rarely test production parts, a few things like lasers maybe. We have to read data sheets carefully (and skeptically) to really understand the parts. We sometimes test a few parts, or breadboard sub-circuits, if we're not confident that we fully understand them.

We can re-use parts of a design at the schematic copy-paste level. We have a "template", schematic and PCB layout, for some boards that plug into a common backplane.

We do extensive first-article testing on an assembled product, and every production unit gets automated test and cal. You don't have to calibrate software!

Software doesn't break like hardware can, but it can run in all sorts of environments with all sorts of inputs. So it does break.

I guess people still use FP libraries when the hardware doesn't do FP. But do people still write their own? Scary.

I wrote one (68K cpu) math library where everything was signed 64 bits, as 32.32. No normalizing for add/sub! 32.32 is enough for representing physical reality.

I started building my own stuff very early on. PRoblem was, I took what I had learned in physics class literally. Well, initially. Like that capacitors are ideal components. Until one fine day the fluorescent lights in my room dimmed and I new they weren't dimmable. What the heck? Huh? ... *POP* .. WHOOOSH ... hisssss

That was one of the electrolytics that had turned itself into a missile and whizzed by inches from my left eye. Whew! I learned about ESR the hard way. It took some plaster out of the ceiling and after return to earth melted an ugly splotch into the carpet.

Bingo! Exactly what I did.

I had pretty bad grades because I worked a lot on the side, did "pre-degree consulting" and stuff like that. Bad grades are ok.

I am currently on a no-booze phase, to lose weight. Exercise alone ain't cutting it.

Oh, you know a LOT about them; the confluent hypergeometric functions are general forms that (when you fill in constants) make ALL the familiar functions (as well as a lot of unfamiliar ones).

A (typical) homework assignment in that subject would be to tell what the common names are to a few example confluent hypergeometric special cases.

It wouldn't surprise me if you could get a CHF to generate Gray codes.

Board revisions and chip mask revisions are visibly high cost.

I find it ironic that you rail against software developers and yet trust making your hardware designs based on the output of software simulators.

Some software is actually pretty reliable (and unlike hardware it tends to become more reliable the longer that it is used for and bugs get found and eliminated). We tend to notice the stuff that *doesn't* work.

In an honest system, bad grades mean that the student either didn't do the work, or was unable or unwilling to do it well. There can be lots of reasons for that, such as being unavoidably too busy, but that's not the usual case.

The result is wasted time and money, and usually a skill set that's full of holes and harder to build on later. It sounds like you were sort of making up your own enrichment curriculum as you went on, which is a bit different, of course.

I knew some very smart folks whose grades were poor, but they were mostly unmotivated or undisciplined. One guy (a math genius) was in my grad school study group for awhile, but was way too handsome for his own good--he spent his time playing soccer and chasing women, and tried to skate by on talent as he'd always done. Eventually it stopped working. If you go far enough, it always does.

That's the real benefit of weed-out courses--not that many people flunk, but that the ones who succeed have to learn to learn mental discipline in the process. That'll stand you in good stead for a lifetime. (Flunking isn't the worst thing that can happen to you. I got fired from my first job, which was very beneficial overall.)

Students sometimes ask me for advice, and I always tell them three things: first, in every field, make sure you have the fundamentals down cold; second, concentrate your course work on things that are hard to pick up on your own, especially math; and third, join a research group where you can do a lot of stuff on your own. (The ideal is to have an interesting smallish project, where you have to do everything, and a bunch of smart and supportive colleagues.)

That's the most direct path to wizardhood that I know about.

Cheers

Phil Hobbs

Do you mean FPGA test benches? An FPGA is just a tick-tock state machine; it's not hard to get that right. The hard blocks inside an FPGA, things like PLLs and serdes blocks, must be well tested or they couldn't sell the chips.

Most progrmmers don't know what a software state machine is. I explain them and they are amazed, or stunned. They write multi-thread procedural hairballs with async inputs and depend on system calls that someone else wrote. They are trapped in a very thin abstraction layer. I ask embedded programers "how long does that take to execute" and "what frequency can we run that interrupt routime at" and they have no idea. They bail on the first and tend to gr

My first pld-type projects were one-time fuse devices, PALS programmed in PALASM and Actel antifuse devices with schematic entry. There were no simulators and no easy retries, so we just got things right first pass. My digital delay generators use an instant-start oscillator as the delay time base. It's instantly phase-locked to a different-frequency crystal oscillator, preserving the phase of the external trigger but has the XO's quality. Hairy DPLL. The first unit used an antifuse OTP soldered-down FPGA and worked first time.

Just be careful and check your work before you run it. That's why bridges seldom fall down.

Sure it's reliable after the bugs are worked out. Unless someone goes out of business or the plane crashes.

I should add that "good grades" don't always mean A/A+. The US educational system has long had this tendency to reward letter-perfect regurgitation over understanding and independent thought. That's very prevalent in K-12 but less so in university. Still, one might be better off taking one more course per semester and not being letter-perfect.

Stanford was/is on the quarter system, so you have more choices.

Cheers

Phil Hobbs

I really lost interest in attending university lectures after a few things were taught by professors that were profoundly wrong. The first one was that RF transmitters must have an output impedance equal to the impedance of the connected load or cable. The week after I brought in the schematic of a then-modern transistorized ham radio transceiver and pointed out the final amplifier. The professor didn't really know what to say.

Number two: The same guy said that grounded gate circuits in RF stages make no sense at all. Huh? I did one of those during my very first job assignment when the ink on my degree was barely dry. And lots before as a hobbyist.

Number three: Another professor said that we only need to learn all this transistor-level stuff for the exam. Once we graduated this would all be obsoleted by integrated circuits. That one took the cake. Still, it seemed I was the only one who didn't believe such nonsense. However, it provided me with the epiphany "Ha! This is my niche!". And that's what it became. Never looked back.

This was at a European ivy league place which made it even more disappointing.

My dad hinted that I was a bread scholar who'd only learn something if it can be put to profitable use, and prontissimo. For the most part he was right.

Agree, it makes the students tough. Just like military service does. When I was at boot camp I really resented being in the Army, life was hard, sergeants screaming in our faces, and so on. Later in life I realized that it had taught me a lot that I use to this day.

I think a job is very educational. In Germany we had to do a minimum of six months of "relevant industrial practice" for a masters degree. Sort of internships, during our studies. Three of those months had to be completed by the 4th semester. It could not be all at one place but AFAIR at four companies. The jobs had to be meticulously documented. These documents had to be turned in and the university had to approve them or it wouldn't count. Not always easy. Two of mine were in a foreign language (to them) and they gave me some grief about that.

They did away with that requirement which I think was a major mistake.

I did some other bigger jobs also and at some point was a taxpayer in three different countries. That alone is a teachable situation.

Another upside of this is that you don't finish university with a chunk of student debt but with savings in the bank.

[...]

I have never attended any American schools other than some snippets of open learning (without credits) but I have interviewed lots of candidates. US and Canadian Universities seem to be pretty good and IME it doesn't make much of a difference whether that was a small local one or ivy league. US schools OTOH often seem to be the pits. Many kids can't even spell correctly or understand math. Except kids from non-public schools like home-schoolers, charter or parochial. A surprising number of good job candidates had a Jesuit High background. They must be doing something right.

As long as there are John Wayne movies :-)

Although you can get most of those on the Internet and then also in libraries.

I wish we had a geostationary satellite in the US but I don't think there is any chance in the near future.

Not here. It's all payola. Well, not for our family. If our TV ever croaks I don't think we are going to replace it.

You have a better system. Less resolution but better multipath tolerance. Ours seems to not have been tested well in suburbian settings. Yet that is where people with disposable income live. Plus they voluntarily gave up VHF frequencies which was a big mistake. I told a station manager here that all this would result in diminished ad volume and later "personnel adjustments" (code for layoffs). He didn't believe me. Then it happened.

I've been in Europe a few years ago and the relative I stayed with has satellite TV. A bazillion channels. What I saw there only elicited the same reaction as the 200 channels in hotels here, a big yawn.

Yup, analog. Although CW is technically a "digital mode". That's >95% of what I am doing, using squeeze paddles and the computer between my ears.

umm "The first one was that RF transmitters must have an output impedance equal to the

I am not an 'RF' guy but have dabbled with ham radio designs, and did do audio amp designs. I clearly remember circuit analysis being done to ensure that impedance matching was done because it is essential for maximum power transfer. So how is that wrong? The fact that you had a counter example doesn't make the theory wrong, just the counterexample.

On the third point, I don't think he was wrong, just very narrow minded. In one of my digital logic design courses various methods of gate minimization' were beat into us (K-maps, prime implicates, etc). Thought it was foolish, after all, IC gates were cheap, fast, plentiful. Twenty years later I remember doing gate minimization for PALs....

On a sunny day (Tue, 10 Jan 2023 15:12:41 -0800) it happened Joerg snipped-for-privacy@analogconsultants.com wrote in snipped-for-privacy@mid.individual.net>:

Less resolution? Its all HD here now since DVB-T2

# mediainfo NPO_2-20230110203002-.mts General ID : 2310 (0x906) Complete name : NPO_2-20230110203002-.mts Format : BDAV Format/Info : Blu-ray Video File size : 1.88 GiB Duration : 1 h 0 min Overall bit rate mode : Variable Overall bit rate : 4 490 kb/s

Video ID : 7021 (0x1B6D) Menu ID : 720 (0x2D0) Format : HEVC Format/Info : High Efficiency Video Coding Format profile : Main@L4.1@Main Codec ID : 36 Duration : 17 h 35 min Width : 1 920 pixels <----------------- Height : 1 080 pixels <----------------- Display aspect ratio : 16:9 Frame rate : 50.000 FPS <----------------- Color space : YUV Chroma subsampling : 4:2:0 (Type 0) Bit depth : 8 bits Color range : Limited Color primaries : BT.709 Transfer characteristics : BT.709 Matrix coefficients : BT.709

Audio #1 ID : 7022 (0x1B6E) Menu ID : 720 (0x2D0) Format : AAC LC SBR Format/Info : Advanced Audio Codec Low Complexity with Spectral Band Replication Commercial name : HE-AAC Format settings : NBC Muxing mode : LATM Codec ID : 17-2 Duration : 1 h 0 min Bit rate mode : Variable Channel(s) : 2 channels Channel layout : L R Sampling rate : 48.0 kHz Frame rate : 23.438 FPS (2048 SPF) Compression mode : Lossy Delay relative to video : -609 ms Language : Dutch

VHF? more like UHF! 474 to 626 MHz or so:

Well you gotta find the gold in the dirt... Some things I really like, like the repair shop on BBC1, afternoon at around 4 PM UTC .. fixing old things, maybe because I had a repair shop. Those guys are good and I still learn from it. There is so much more to broaden your view, much better than 'the weather is cloudy here' ...

Well my Morse sucks, SOS I know, you can use software to code and decode from text these days I think.

Sat goes to UHD (Utra High Resolution, 4 k) there are already some test transmissions.. My TV cannot do that, and at my age at the normal viewing distance I doubt I would see much difference, You would need a BIG screen, no space for that. HD at 1920x1080 is already amazing, see every hair on someone's face,,, Also at UHD the recordings get much longer .. need more disk space. So a movie becomes like 128 GB.. The cheap sat boxes I use simply record to a 128 GB or 64 GB USB stick. Those use some old windows format, so every few GB it starts a new entry... I can read those files on the PC or laptop and 'cat' those together on a real Linux filesystem to get one big file. I have mostly stopped storing things now on optical, Bluray... All SDcards now... The box was full with 1000 disks,

On a sunny day (Tue, 10 Jan 2023 14:57:00 -0800) it happened Joerg snipped-for-privacy@analogconsultants.com wrote in snipped-for-privacy@mid.individual.net>:

Sure, used those in some projects.

In my school, a teacher (old one) was teaching us about transistors. Transistors most of us were experimenting with at home.. So one guy asked; 'Sir what exactly is a complementary pair?' Teacher got furious, thought it was a sex joke, and asked the guy to leave.. It took the whole class (most of use knew the answer) to convince the teacher that that was a legitimate question. Early sixties that was... I think that teacher never had a transistor in his hands,, mostly lived in the tube ages. Lucky we also had an other teacher who knew what he was doing..

The maximum power transfer thereom is about getting maximum power from a supply with internal impedance- not about getting maximal power into just the load.

piglet

I have made a VHDL triple module redundancy library that looks much like std_logic, std_logic_vector, un/signed and has mostly all error detection / correction hidden under the hood.

It was really hard to convince the VHDL compiler not to optimize away badly needed parts of the circuit. A possible factor 5 reduction in CLBs spawns endless efforts.

Sometimes, it took the use of inputs where only me, myself & I knew the value of.

But then it is wonderful to see that you inject multiple SEU errors per clock into a counter and it continues completely unimpressed, in Terminator style :-)

Gerhard

[...]

Joerg is right. The usual design path for an RF transmitter power stage is to calculate the load resistance needed to obtain the required output power, assuming the peak-to-peak output is 2*Vcc. An impedance transformation is then inserted to transform the actual 50 Ohm load to that resistance. Looking back into the transmitter output, the source impedance is then not at all equal to 50 Ohms.

There are application notes written by Helge Granberg that explain this very nicely.

Jeroen Belleman

Well, I've never taken a circuits class, so I may have dodged a bullet or two of that sort. ;) (*)

I don't recall ever being told what would or would not be important in my future career, but maybe I just didn't listen.

Sounds super cumbersome. I can't imagine getting the sort of industry buy-in that that would require. I knew a fair number of EE co-op students at grad school, both from business and from the military, and the DSP course had a live video feed to some companies' sites, which was fairly novel in 1985. (They were mostly defence contractors IIRC.)

Yikes.

Because I started university youngish, I had time to do a gap year and then worked for a couple of years at a local telecoms place (Microtel) where they really chucked me in the deep end. Very educational indeed.

(*) I did take the required "RLC for physicists" class as a sophomore, which talked about resonance, damping factors and so on.

Cheers

Phil Hobbs