Thank you. I'm aware of the quadrature type of stuff (nowhere near an expert or competent) but I wasn't even going to extend the 'argument/debate' into "Well, there even are instances where the clock signal of a PC is used to accomplish, what I believe it is called, 'quad-pumping' the CPU. It is a term that I read long ago which explains how the CPU (or front side bus) can identify four states from the main clock signal and such as: 'we are steady at zero', 'we are increasing in voltage', 'we are steady at one', 'we are now again descending in voltage' and you can get faster timings that way. That is how I understood it to work anyway.
This is correct. The steepness of the "cliff" is a function of the type of Error Correction Coding (ECC) used in the system. All modern digital communication waveforms employ some form of ECC where "extra" bits are used to reconstruct data lost to noise. Stronger (more complex) coding schemes can correct more errors and have better performance under noisy conditions (low signal-to-noise ratios). The stronger the ECC, the steeper the drop off when it finally starts to fail.
I can agree with that. Where the end result, the goal, is the reconstruction of a digital signal but from waves that are not 'electromagnetic square waves' as my friend insisted. I would find it very interesting if a different 'method' was used and EM square waves were tried to be sent and then some kind of 'active' antenna would have to sync up with the clock rate of those square waves and skew would happen and it just wouldn't work, heh.
Whoa! Nice!!!
I've got some studying to do on those graphs and the QAM topic. Like I mentioned in my other thank yous (and thank you to ALL here), I've glossed over QAM but I'm just a computer programmer whose father taught him the basics about speaker building and gave me books that told me about guys like Thiele and Small (I wish I knew much more about electrical engineering too!). There once was a time when my comcast signal was all haywire and after repeated attempts by comcast to fix it, I tried to study it (their purported signal sent out) myself. That's where I ran into QAM. I then just did 'my part' (meaning in the home from the demarc point) which was checking and rechecking each and every coax cable run for 'as close to perfection carrying the highest frequency signals' as possible. If the technician said to use quad-shielded coax or something, fine, not a problem (I'm already used to running tons of feet of CAT5/6 cabling and putting the connectors on myself so I did my part and eventually the problem was solved). It was the run from across the street, under the street, and their cable had become damaged (and not by me). So, they ran a new cable and, what do ya know, it worked, heh.
I cannot say that, with a straight face, to my friend who bought the 'digital antenna', hehe.
But, I've always known that the people on diyAudio are vastly knowledgeable and that is what makes this site so awesome. I wish I hadn't been away for so long.
I think a digital optical signal can be perfect: light pulse/no light pulse. As soon as it is converted to electrical signal, it is not perfect any more.
Many people will accept without question the lies and distortions of marketing people, while summarily rejecting the claims of experts like engineers that actually design the products.
Muricans are stupid and getting stupider. That's what makes Murica great.
That is cool and so many people, from what I have found (not speaking for everyone here), don't appreciate the older items.
I just went and grabbed the 'manual' contained in one of quite a few very old radios, CB's, Bearcats, etc that my father left to me. He was into HAM radio at our first house (I barely remember those days). He got away with having that large rectangular box looking wireframe and high up on a post antenna for quite a few years until we moved (when I was still quite young) and it was 'disallowed' from being 'reconstructed' at the new home's backyard (booooooo, I would say).
It is a Zenith Trans-Oceanic Clipper model no. 8G005. It has pages of his 'radio logs' handwritten in the provided grid spaces. I fire that up only once or twice a year nowadays because I don't want it to completely fail (there aren't tubes still around for these, are there???).
My father taught me how to 'tune in distant signals' when I was quite young but yet not having an awesome antenna. Remember the movie "Contact" (Jodie Foster) and when she was trying to tune in signals as a youth? When I saw that movie long ago, I was transported back to when me and my dad would try to tune in signals. But, I could not 'transmit' with this Zenith unit.
Great memories. Learning about how signals could bounce around the Earth and all that from him...
I also have my grandfather's (my father's father) OLD radio (kind of like how you described your old radio), I demanded it be mine after he and grandma passed, no one could understand why, but it was because it was always tuned into WCCO I believe and that sound sequence of "doo doo doo do do do, beep, beep, beep, beep, beep' fading off would sound while I was over there. That meant a new 'segment' was starting or something.
You can build TTL logic circuits with a handful of cheap cheap transistors, diodes, and the cheapest of the cheap resistors.
My friend was amazed when she saw I built a computer control circuit that doesn't need software, and never glitches. Welcome to 1975.
My friend was amazed when she saw I built a computer control circuit that doesn't need software, and never glitches. Welcome to 1975.
In reality, no. Where the light source is a semiconductor LASER, it has it's own dynamic response (due to the physics of conversion of electrical input to light) such that it cannot turn instantaneously 'on' or 'off', and the driving electrical signal has a finite bandwidth too. So optical 'eyes' are very similar to electrical ones, e.g. (from public domain):
As long as the 'mask' (purple polygon) is not voilated with the traces, the receiver can discriminate between the '1' and '0' levels to reconstruct the transmitted digital data.
That is EXACTLY how I always felt. I do not get into marketing/advertising AT ALL. When CD players first came out, and I was a young kid still, I looked at all the models on display at Best Buy, the salesperson (think 1980's and pastels worn) started his schpiel, and I just said "I want the manuals and specifications for these three models." and he asked WHY?! He hadn't read a really great book by Ken C. Pohlmann named "The Compact Disc Handbook (2nd ed)". I just retrieved it from my library. Taught me what CD players should be able to do soundwise and what was likely not very truthful, hehe. Also, started the path on how to extract all of the samples perfectly so really fun custom DSP functions could be run on the extracted tracks!
Remember Intel's CPU's with the 'new MMX instruction set' from long ago?
It wasn't useful, except to perhaps the Windows OS, when upgraded after recompilation by Microsoft, because all the other software companies would need to rewrite and recompile THEIR main products to take advantage of the new instructions.
So, us tech guys back then called/joked-about MMX being "Marketing Magic in eXecution", heh.
Now, being a programmer, YES, it is nice to get those new instructions but while I could and can rewrite my own software to take advantage of even today's best instruction sets (even from a DSP project started back in 1989), I could not and still cannot demand that big software companies do the same and give me the upgrade for free, heh.
Like I made mention of earlier, I've got some studying to do (because I love this stuff).
And your introduction of optical sources....now you're way over my head, hehe.
To expand on it: "Digital" signals are so, and depend on almost perfect squarewaves or pulses, because they are all the time Reconstructing the squarewave.
...the world is 'analogue' until such time that we can actually figure out that atoms and particles, when doing their thing, spinning and orbiting, do have a 'clock rate' and they do 'step along' at some rate, right?
Kind of like how time-slicing works with 'multitasking operating systems'? That is most usually an illusion unless multiple cores are involved and they can provide information to the system and the screen all simultaneously without collisions.
And, I don't think I'll ever see that atomic clock discovery in my lifetime.
Not to get off-topic too much but...
...the world is 'analogue' until such time that we can actually figure out that atoms and particles, when doing their thing, spinning and orbiting, do have a 'clock rate' and they do 'step along' at some rate, right?
Kind of like how time-slicing works with 'multitasking operating systems'? That is most usually an illusion unless multiple cores are involved and they can provide information to the system and the screen all simultaneously without collisions.
And, I don't think I'll ever see that atomic clock discovery in my lifetime.
If you want to generate PCM square wave test tones, you have to use additive synthesis to limit the harmonics to below fs/2. Anything over that will alias.
Square waves are where a hardware signal generator is better than any test tone CD.
BTW, TTL was great. I used to put together TTL chips like Tinkertoys.
Ed
Square waves are where a hardware signal generator is better than any test tone CD.
BTW, TTL was great. I used to put together TTL chips like Tinkertoys.
Ed
fs/2 is the so-called Nyquist Frequency in your example, right?
And, by using a hardware signal generator, I'm assuming that is something much more specialized and accurate than a run-of-the-mill Realtek ADC/DAC, of lesser capability, trying to generate the square waves?
I remember accidentally 'aliasing frequencies' by breaking the fs/2 rule (not setting the sampling rate high enough while 'remastering' my inherited and old reel to reel tapes), and I believe those highest frequencies would then 'wrap around' to being the lowest frequencies and I could see my woofers move in and out at a rate from like 5 to 15 cycles per second, heh.
There is a very specific song/track by a very industrial band. The CD is from around 1993. The last track causes woofers to move in and out at a very slow rate. Don't know to this day if that European band did that on purpose.
I remember arguing with a co-worker who wouldn't back down from his claim "CDs are 100% perfect in any way." My "boss" had exactly the same misconception.
Marketing is just as corrosive to intellect as religion. Marx was spot on when he said "religion is the opiate of the masses."
I just got out of the hospital. They fed me a steady cocktail of drugs "the good stuff" through the IV. I could literally feel my intellect fading as the drugs coursed through my system (not an unpleasant feeling, especially when it's quelling the searing pain of post surgery.) I can see the same thing happening to people when exposed to marketing lies and religious drivel. "YOU MUST BUH-LEAVE." It's like free and legal morphine. Repeated exposure will permanently dim your intellect. Exhibit A; Murica.
I think the point has already been made, but I can offer an interesting example. I worked on a gigabit ethernet chip in the early 2000s. Each pair of cat 5 carries 250 Mb/s and at the transmitting side there are 21 different levels that are sent, not just low and high. At the receiver side, after the signal is equalized it is sampled (at 125 Ms/s) and converted from analog to digital. The resulting digital word represents the analog value of the signal at the sampling time (sampling at the correct times is very important). Then DSP is used to sort out the bits that were most likely to have been sent. Other blocks accomplish crosstalk cancelation and maximum likelihood sequence detection. It's surprisingly complicated.
If only a low or high was sent, and the receiver had to wait for the signal to settle to something close to its sent value, the data rate would need to be much slower.
Tom
If only a low or high was sent, and the receiver had to wait for the signal to settle to something close to its sent value, the data rate would need to be much slower.
Tom