Another Dumb-phuk Wrote Him Uh Buk
I was working on a project last night, and considered using the material from this book: Analog and Digital Filter Design -- a second edition, no less. This is important later.
Here's the back cover and a bio of this dumbass:
Makes him look like some sort of hot-shot, doesn't it? It's like I've always said: "A minimum wage burger slinger, counter man at the corner 7-11, Wal-Mart greeter has far more responsibility than any asshole making ten times as much". That applies to this dipshit, Steve Winder, in spades. Here's what I found on page 415:
I know, I know: you're probably wondering what this us about. Take a look at the part in red. Let's do exactly what he says:
Set R= 4 (It doesn't matter)
Then do the calc: enter that in your scientific calculator (make sure you're set up for radians, not degrees).
(cos((4*pi)/(2*4)))^2= 0
That's right: you get a nasty divide by zero error when you go to compute what C4 is supposed to equal. If your telecommunications devices don't seem to work right, then you can be sure Steve Dipshit here designed it. How can you be so fucking stupid? Doesn't this dumbfuck use his own damn formulas? Don't they have proof readers to catch mistakes like this?
I looked into this problem, and here's the correct results:
br= cos2[(R-1)π/2n] You're welcome.
Remember: this is a second edition, you know, the one that followed the first and corrected the typos and dumbassed shit like divide by zero errors.
And Another One
Another dumbfuck has emerged from the swamps of academia. This time, an extract from a text written by a kollidge perfesser. Here's the introduction to this particular chapter:
"Thuh taybuls is noo han rekruhzent thuh stayt of thuh hart hin muh-sheen kalkulahmayshuns". Here's the table of Bessel coefficients:
Here's the results from running the tenth order coefficients through MPSolve:
Wrong! Wrong! Just plain FUCKING wrong! Poles that lie inside the right hand half plane always represent instability. If your transfer function is that of passive components only, this is not possible. If there are active components, then these poles with positive real components means that your amp/filter/whatever has just become an oscillator. Also notice that there are two first order poles with real parts only. This, too, can not happen for any polynomial that actually describes a transfer function. Two first order systems != one second order system. No legitimate transfer function will ever have more than one first order system, and then only for odd numbers of poles.
Just looking at the table of coefficients should have clued this dumbass that his "muhsheen" was malfunctioning. From the table, c3, c5 and c7 are actually larger than the next higher order coefficient. Bessel coefficients are inversely proportional to the order. That is an obvious error.
You see this again in the Order 9 list. Even though Order 8 looks OK, this one is still fucked up. Bessel coefficients aren't hard to calculate; it's just tedious as hell, so I recalculated them the old fashioned way: with pencil, paper, and a scientific calculator. Here are the correct coefficients:
Bessel Coeffs for Order= 10
Coefficient
Value
c0
654729075
c1
654729075
c2
310134825
c3
89864775
c4
18918900
c5
2837835
c6
315315
c7
25740
c8
1485
c9
55
c10
1
Bessel Coeffs for Order= 9
Coefficient
Value
c0
34459425
c1
34459425
c2
16216200
c3
4729725
c4
945945
c5
135135
c6
13860
c7
990
c8
45
c9
1
Bessel Coeffs for Order= 8
Coefficient
Value
c0
2027025
c1
2027025
c2
945945
c3
270270
c4
51975
c5
6930
c6
630
c7
36
c8
1
You're welcome.
Remember, your keeds are "learning" Lektikal Injuneerin from these texts, taught by dumbassed stoodunt 'sistunts for the most part (kollidge perfessers spend most of their time pursuing Uncle Sugardaddy's grant money -- our money, collected as taxes). And people wonder why there's such a big demand for ancient, vacuum tube based electronics. Now you know why: all this modern electronics was designed by engineers who "learned" their trade from clueless dumbfucks that wrote books according to the standards of academia: "Publish or perish", and its corollary: "If you can't dazzle them with brilliance, baffle them with bullshit".