The $50 Ham: Getting Your Ticket Punched

Today we start a new series dedicated to amateur radio for cheapskates. Ham radio has a reputation as a “rich old guy” hobby, a reputation that it probably deserves to some degree. Pick up a glossy catalog from DX Engineering or cruise their website, and you’ll see that getting into the latest and greatest gear is not an exercise for the financially challenged. And thus the image persists of the recent retiree, long past the expense and time required to raise a family and suddenly with time on his hands, gleefully adding just one more piece of expensive gear to an already well-appointed ham shack to “chew the rag” with his “OMs”.

Not a $50 ham. W9EVT’s shack. Source: QRZ.com

As I pointed out a few years back in “My Beef With Ham Radio”, I’m an inactive ham. My main reason for not practicing is that I’m not a fan of talking to strangers, but there’s a financial component to my reticence as well – it’s hard to spend a lot of money on gear when you don’t have a lot to talk about. I suspect that there are a lot of would-be hams out there who are turned off from the hobby by its perceived expense, and perhaps a few like me who are on the mic-shy side.

This series is aimed at dispelling the myth that one needs buckets of money to be a ham, and that jawboning is the only thing one does on the air. Each installment will feature a project that will move you further along your ham journey that can be completed for no more than $50 or so. Wherever possible, I’ll be building the project or testing the activity myself so I can pursue my own goal of actually using my license for a change.

Continue reading “The $50 Ham: Getting Your Ticket Punched”

Musical Mod Lets MRI Scanner Soothe the Frazzled Patient

Hackers love to make music with things that aren’t normally considered musical instruments. We’ve all seen floppy drive orchestras, and the musical abilities of a Tesla coil can be ear-shatteringly impressive. Those are all just for fun, though. It would be nice if there were practical applications for making music from normally non-musical devices.

Thanks to a group of engineers at Case Western Reserve University in Cleveland, there is now: a magnetic resonance imaging machine that plays soothing music. And we don’t mean music piped into the MRI suite to distract patients from the notoriously noisy exam. The music is actually being played through the gradient coils of the MRI scanner. We covered the inner working of MRI scanners before and discussed why they’re so darn noisy. The noise basically amounts to Lorenz forces mechanically vibrating the gradient coils in the audio frequency range as the machine shapes the powerful magnetic field around the patient’s body. To turn these ear-hammering noises into music, the researchers converted an MP3 of [Yo Yo Ma] playing [Bach]’s “Cello Suite No. 1” into encoding data for the gradient coils. A low-pass filter keeps anything past 4 kHz from getting to the gradient coils, but that works fine for the cello. The video below shows the remarkable fidelity that the coils are capable of reproducing, but the most amazing fact is that the musical modification actually produces diagnostically useful scans.

Our tastes don’t generally run to classical music, but having suffered through more than one head-banging scan, a half-hour of cello music would be a more than welcome change. Here’s hoping the technique gets further refined.

Continue reading “Musical Mod Lets MRI Scanner Soothe the Frazzled Patient”

Hacking high school exams and foiling them with statistics

graph

A few weeks ago, [Debarghya Das] had two friends eagerly awaiting the results of their High School exit exams, the ISC national examination, taken by 65,000 12th graders in India. This exam is vitally important for each student’s future; a few points determines which university will accept you and which will reject you. One of [Debraghya]’s friends was a little anxious about his grade and asked if it was possible to hack into the board of education’s servers to see the grades before they were posted. [Debraghya] did just that, and was able to download the exam records of nearly every student that took the test.. Looking even closer at the data, he also found evidence these grades were changed in some way.

Getting the grades off the CISCE board of education’s servers was very simple; each school has a separate code, and each student is given an individual number. With the simplest javascript magic, [Debraghya] discovered that individual grades could be accessed by pointing a script to /[4 digit school ID]/[3 digit student ID] on the CISCE server. There was absolutely no security here, an impressive oversight indeed.

After writing a small script and running it on a few machines, [Debraghya] had the exam results, names, and national IDs of 65,000 students. Taking a closer look at the data, he plotted all the scores and came up with a very strange-looking graph (seen above). It looked like a hedgehog, when nearly any test with a population this large should be a continuous curve.

[Debraghya] is convinced he’s discovered evidence of grade tampering. Nearly a third of all possible scores aren’t represented in the data, but scores from 94 to 100 are accounted for, making the hedgehog shape of the graph statistically impossible. Of course [Debraghya] only has the raw scores, and doesn’t know exactly how the tests were scored or how they were manipulated. He does know the scores were altered, though, either through normalizing the raw scores or something stranger and more sinister.

While scraping data off an unencrypted server isn’t much of a hack, despite what the news will tell you, we’re awfully impressed with [Debraghya]’s analysis of the data and his ability to blow the whistle and put this data out in the open. Without any information on how these scores were changed, it doesn’t really change anything, and we’ll welcome any speculation in the comments.