Wikipedia:Reference desk/Archives/Computing/2011 November 29

= November 29 =

Radio Transmittion
Which sort of transistor does one install to increase reception amidst the shortwave bands? — Preceding unsigned comment added by Denting5 (talk • contribs) 00:51, 29 November 2011 (UTC)
 * It can't be done with just "a transistor". You firstly need to know why the signal is poor, diagnosing some of the possible problems requires fairly sophisticated signal measuring and analyis equipment. Then you can apply an appropriate solution which could be one or more of the following: a better antenna, a pre-amplifier, better filter stages, and others. If a better antenna doesn't cure it you basically end up redesigning the receiver. Joining an Amateur radio club and taking the courses they offer would be the "short answer". Roger (talk) 19:36, 29 November 2011 (UTC)


 * If you are designing your own radio, you will need a front-end transistor which has a low noise, good third order intercept point, (to reduce distortion which creates interference by mixing strong signals together), and good stability so that it amplifies the same amount even if the temperature varies. However if you are going to buy a transistor radio you will need to select one with coverage of the frequency bands you want.  I recommend a digitally frequency synthesised model with digital readout of the frequency.  If you want to receive single side band or Morse code make sure it has a beat frequency oscillator. Graeme Bartlett (talk) 21:30, 3 December 2011 (UTC)

The backwards E that will not go away
Referring to this question and others that preceded it, I have returned to the library where that computer is. The woman who works there said she didn't know what was wrong, so apparently someone checked it out. She blamed the web site but the problem is independent of what web site I'm on. It does appear to be nothing more than the cursor turning into this thing, and not something more serious.

I was asked what computer I was on. It says HP. I don't know what software it has, but it seems to be some type of IE. Vchimpanzee ·  talk  ·  contributions  · 14:27, 29 November 2011 (UTC)
 * I forgot, did you ever look at the list of cursors (if it's possible with whatever admin restrictions the computer has) to see if it's there? Nil Einne (talk) 16:36, 29 November 2011 (UTC)


 * What Nil Einne appears to be getting at is that some nefarious user could replace a cursor icon with something silly, like a backwards E. I also noted that it is not really a backwards E. It is a standard text selection cursor (the vertical line with a bar on top and bottom) with a backwards E overlayed on it. -- k a i n a w &trade; 17:17, 29 November 2011 (UTC)


 * Try navigating to C:\Windows\Cursors\ and see if any cursors have the backwards E. TheGrimme (talk) 18:54, 29 November 2011 (UTC)
 * Also, in Internet Explorer (the browser where the E appears), try going here and hover the mouse over the different cursor types. See if one of them causes the E to appear. TheGrimme (talk) 19:00, 29 November 2011 (UTC)


 * I wasn't necessarily suggested it was a nefarious user, it could be set up by the system admins, although the fact it only appears on one computer means it's likely. If you go to the Control Panel you and find the mouse properties and view it there should be a pointers which would show those set up in Windows. I can't remember the specifics of how to get there for XP and in any case I think 82 or someone gave them previously. As I mentioned admin restrictions may stop you viewing these. Nil Einne (talk) 04:16, 1 December 2011 (UTC)

After looking at the photo posted in the earlier thread, I'd have to say it looks more like a cursor animation error due to a clipping problem. There are any number of complicated, possible root-causes; a faulty graphics accelerator driver is very likely. Nimur (talk) 19:22, 29 November 2011 (UTC)


 * Is is just me that finds this long dragged out obsession with an apparently harmless inconsequential quirk in a computer that the OP doesn't own or have any responsibility for, to be more than just a little wierd. Roger (talk) 19:41, 29 November 2011 (UTC)


 * :D Reisio (talk) 08:51, 2 December 2011 (UTC)


 * Generally when you can't explain a problem that only occurs on one computer, its the computer's hardware and the software communicating with the hardware (drivers) not communicating correctly... In other words the computer is borked and trying to reference something that it shouldn't normally. -  ʄɭoʏɗiaɲ  τ ¢  19:47, 29 November 2011 (UTC)
 * I won't be back at this library for another week, and I lost that particular computer before I got these answers, but I'll see what I can do. Vchimpanzee ·  talk  ·  contributions  · 20:31, 29 November 2011 (UTC)

LaTeX: Align matrices across lines
Is there be any way to get the matrix columns, bars and brackets in these two equations to line up, without having to split up the matrices and specify the bracket/bar heights manually? I've tried inserting &'s in the inner arrays' column lists like this:  But that just gives an error. Neon Merlin  23:44, 29 November 2011 (UTC)

\[ \begin{array}{cccccclcl} \left[ \begin{array}{c|c} \textbf{A} - 8\textbf{I} & \overrightarrow{0} \end{array} \right] &=&          \left[ \begin{array}{cc|c} -8 &            2 & 0 \\ 8 & -2 & 0 \end{array} \right] &\rightarrow& \left[ \begin{array}{cc|c} 1 & -\frac{1}{4} & 0 \\ 0 &  0 & 0 \end{array} \right] &\therefore& E_8 &=& \operatorname{span} \left( \left[ \begin{array}{c} 1 \\ \frac{1}{4} \end{array} \right] \right) \\ \left[ \begin{array}{c|c} \textbf{A} + 2\textbf{I} & \overrightarrow{0} \end{array} \right] &=&          \left[ \begin{array}{cc|c} 2 & 2 & 0 \\ 8 & 8 & 0 \end{array} \right] &\rightarrow& \left[ \begin{array}{cc|c} 1 & 1 & 0 \\ 0 & 0 & 0 \end{array} \right] &\therefore& E_{-2} &=& \operatorname{span} \left( \left[ \begin{array}{c} 1 \\ -1 \end{array} \right] \right) \end{array} \] $$\begin{array}{cccccclcl} \left[ \begin{array}{c|c} \textbf{A} - 8\textbf{I} & \overrightarrow{0} \end{array} \right] &=&          \left[ \begin{array}{cc|c} -8 &            2 & 0 \\ 8 & -2 & 0 \end{array} \right] &\rightarrow& \left[ \begin{array}{cc|c} 1 & -\frac{1}{4} & 0 \\ 0 &  0 & 0 \end{array} \right] &\therefore& E_8 &=& \operatorname{span} \left( \left[ \begin{array}{c} 1 \\ \frac{1}{4} \end{array} \right] \right) \\ \left[ \begin{array}{c|c} \textbf{A} + 2\textbf{I} & \overrightarrow{0} \end{array} \right] &=&          \left[ \begin{array}{cc|c} 2 & 2 & 0 \\ 8 & 8 & 0 \end{array} \right] &\rightarrow& \left[ \begin{array}{cc|c} 1 & 1 & 0 \\ 0 & 0 & 0 \end{array} \right] &\therefore& E_{-2} &=& \operatorname{span} \left( \left[ \begin{array}{c} 1 \\ -1 \end{array} \right] \right) \end{array}$$
 * If it's a one-off case, you could put a \mbox around the parts of the equations that are different, and specify the width of the box (for example, box in the first "2" in the second line with a box that has the same width as the "-8" in the line above). Possibly there exists some code to input the "width of -8" directly, so you only have to specify a box around the shorter part. I'm no expert, but try googling for some \mbox syntax. Jørgen (talk) 13:37, 1 December 2011 (UTC)