Two useful computer tips

Having had two annoying computer issues in the last 24 hours, this is how I fixed them. It’s more a not to myself, but also might get picked up by google and help someone else in the same position.

Corrupt MacOS HDD

The hard-disk in my spare (ancient) MacBook was found to be corrupt. Booting the MacBook from the diskwarrior DVD didn’t work. The diskwarrior software needs more then 1Gig of RAM to run, the ancient MacBook didn’t have this.

Putting the drive in a USB diskcaddy thing and running diskwarrior on another mac computer worked, but diskwarrior claimed there was a hardware failure on the drive. Given I could hear it spinning, and I’d been able to get it to sort-of boot in the MacBook I wasn’t ready to believe it was actually physically dead.

It turns out that the computer I’d connected it too was trying to decide if it could be used as a TimeMachine backup disk. As it was corrupt, it was trying to fsck the disk first – but failing. This was preventing diskwarrior from locking the drive and doing its own low-level recovery. The solution was:

Last login: Mon Mar 31 19:45:28 on console
Curie:~ dm$ ps -ef |grep fsck
0   458   16   0  7:46pm ??  3:12.90 fsck_hfs -y /dev/disk2s2

Curie:~ dm$ sudo kill 458

In other words, find the process “fsck” and kill it. Diskwarrior was then happy and recovered the drive. Yay!

Firefox previous session not restoring

To free up plenty of RAM for diskwarrior to run, I’d closed all the software running on my other laptop. For reasons unknown, Firefox didn’t save my windows and tabs (I have lots of tabs open at any time)

I did have a sessionstore.bak-20140314220517 file in my Firefox profile directory with seemed to contain a list of windows and tabs I remember being open, wrapped up in a bunch of javascript and a sprinkling on html and css.

sessionstore.js in the same place contained pretty much the same code, but without the list of tabs and windows. With nothing to lose, I deleted sessionstore.js and renamed sessionstore.bak-20140314220517 to sessionstore.js. Start up Firefox again and I’m presented with all my lost windows and tabs. Double Yay!

 

Monumental science

It’s not commonly known that the Monument in London was constructed not only to commemorate the great fire, but also as a scientific laboratory. Two of the great scientists of the day, Hooke and Newton performed experiments in basic physics and materials science.
Yesterday evening, some physicists, myself included from Queen Mary University visited with the intention of performing the first experiment at the monument in several hundred years.

image

We were successful!
The real science will start once we’ve made the equipment modifications needed for easier operation in the basement lab of the monument.
More to follow as it happens.

VHF Radio Coverage

I’ve just discovered a nice tool for plotting radio transmission coverage. Here’s where I can expect to get a signal too from my home location.

Where 100 watts of 145 MHz RF will get, from my home QTH
Where 100 watts of 145 MHz RF will get from my home QTH

Yellow shows 0.50 μV signal level, Green is the 1.58 μV signal level

This seems to match up quite well with contacts I’ve had on the two-meter band, but with less power actually used. I’ll have to play a bit more and see how it says my station will perform on other bands.