Recent content by Adoniram

Awesome, thank you for the detailed explanation. I can follow the logic of BPSK, QAM, etc, including error correction and other logic techniques. It was the part where the value was determined to be at +f_BW or -f_BW that was alluding me (or determined to be at some IQ value, etc). Your...

Yes, exactly, sometimes the freq is higher or lower, but how quickly can your hardware determine that? In my ignorance, I feel you'd have to sample some stretch, like maybe 2 or more periods, before knowing the frequency with high confidence. This seems an important feature because complicated...

Hello everyone, I have a question regarding data reconstruction over RF, especially in the case of FM. Let us say I have a trivial case where I have a carrier frequency of fo and a bandwidth of fbw. I want to setup a scheme such that fo + fbw is a 1 and fo - fbw is a 0. (I'm naively under...

Hi everyone, I'm going up for my defense in a few weeks and just wanted to get some insight from others as to what their experiences were like. I've been to many of my colleague's defense presentations, but there is always a ~60 min private session afterwards. Professors are very reluctant to...

Thank you for all that earlier clarification. Regarding this last point, I just don't get why that horizon is drawn there (centered at the space/time origin). It could (theoretically) be drawn from any point on the plot where a photon was emitted, right? The real trouble, for me, was here...

Hi all, I am trying to understand a few basic concepts about cosmology and the CMB, but I am not getting the information presented in these graphics. I've seen them a million times, and I generally just take it for granted without close examination, but now it's bothering me. (these come from...

I often see the phrase "What good is it?" pop up in defending (or attempting to defend) particle physics experiments. Does anyone know who said this, or where this anecdotal story comes from? I've heard conflicting stories about Farraday, or the discovery of the muon or neutrino... The...

Well you do, but you probably didn't know that's what it's called (among students I've known). When you make that substitution to polar coordinates for double (or triple) Gaussian terms in an integral, that's Feynmann's trick. Though I think Griffiths made it popular.

The only problem with that is that r is not always an integer (in fact it almost always isn't). But Feynmann's trick is a good one. Too bad it won't work here.

It's part of a volume sum, not integral. The (i,j,k) values are integer coordinates in a grid, so they cannot be manipulated, or gaps reduced to {\Delta}i (for example) for purposes of integration.

Oops, typos corrected. And actually, this is an oversimplification of the real problem, which is this: \sum_{i=1}^{\infty}\sum_{j=1}^{\infty}\sum_{k=1}^{\infty}e^{-B\sqrt{i^2+j^2+k^2}} So, r is not necessarily integral. If it were, this would converge automatically. However, I was hoping if...

I am trying to manipulate this summation such that I have a summation of a function of r only by itself somewhere: \sum_{r=1}^{\infty}e^{-B⋅r} This could be rewritten: \sum_{r=1}^{\infty}\left(e^{-r}\right)^B or \sum_{r=1}^{\infty}\left(e^{-B}\right)^r What I would like is: f(r)g(B) or...

Let's say I take 3 measurements, and each measurement has its own uncertainty: M1 = 10 ± 1 M2 = 9 ± 2 M3 = 11 ± 3 I want to quote the average, and the net uncertainty. I understand that the uncertainty of the mean is: (Range)/(2*√N) where there are N measurements. So: (11 - 9)/(2*√3) = 1/√3...

Yeah the problem is, it'll never be 1 in reality. It'll be something like (0.05+k)/k which is why it's so hard to invert.

Numerical results are perfectly fine!