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This is a question The B3TA Detective Agency

Universalpsykopath tugs our coat and says: Tell us about your feats of deduction and the little mysteries you've solved. Alternatively, tell us about the simple, everyday things that mystified you for far too long.

(, Thu 13 Oct 2011, 12:52)
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Apologies for length but Prof KM reminded me of this one.
Case of the mystery car stalling on the same corner of the same road.

Back when I was working for a certain car manufacturer there was a request from service to deal with a problem that was occurring with a customer's car and it was practically a case of 'look, I'm telling you it does it' even though the dealer technicians couldn't reproduce it. On the same bend of a road near his house in Aberdeen he claimed his car regularly cut out, leaving him with reduced steering assistance and diminished brake servo. It was serious enough for him to talk about returning his new car.

A buy-back is the worst thing for a car maker's reputation- plus, thanks to the Lemon Law in the states, if word of this got out people would be falling over themselves to claim the same thing so they could in effect 'borrow' a brand new car for a few months and then get their full retail price refund at the end of it.

Now service were baffled and were asking all departments to brainstorm what was going on, and as the diagnostics bloke in the department it fell to me.

First of all I got on to the AA to see how many cars they recovered from that area and what the symptoms were- maybe there's a crop of callouts suspiciously clustered in and around the same area;- but nothing really stood out as the statistical analysis only came to the conclusion that you get more callouts in the winter for non-starts than anything else, and there's less call out the further out of town you go. Rat's cocks. Next.

There was a suspicion that electromagnetic interference could be causing the problem, and despite the fact Google Maps showed 200kV (edited, I originally put 400kV but I've since found my file on the whole thing) power lines nearby, the vehicles have to be tested for electromagnetic immunity at the prototype stage so it would have to be something fairly unusual to cause this. Hang on, this is Aberdeen- don't they have an airport up there?

Out came Google Maps again. Yes indeed there was, Dyce airport. Airports have all sorts of electromagnetic sources, from VHF/UHF communications with aircraft, ILS, taxi cab offices, police radios, staff PMR radios, cellphone towers, observation radar for the runway, interrogation radar and navigational radar. But Dyce airport was a good few miles away, across the valley.

Aha- what's this on the map though? The airport was a few miles away BUT the radar head was actually stuck in a field out near the coast- less than 250 metres from the road where the guy was having his problem! The data from the radar head was beamed back to Dyce using a line-of-sight microwave link so we had a potential extra bogey to suspect.

More intelligence gathering was done- the interrogation radar was microsecond pulses which were designed, when recieved, to make airliners' on-board transponders send a burst back with their ID/altitude/heading information encoded, but the main navigational radar dish operated in the S-Band which was far and above the frequencies that cars are tested to. Suspicious....but surely it points up at the sky, not down at the ground?

Ah well now. The radar 'beam' formed by those 'goal net' parabolic reflectors actually makes a rather curious shaped compound pattern, with 'side lobes' almost perpendicular to the main beam. These emanated in such a way that the lobes may indeed project downwards and 'touch' the ground some 250 metres away where the road was.

Drawing the map and doing some triangulation I went to the boss to explain my theory. The big man thought it was an incredible unlikely story but then there were no other ideas and he almost wanted it to be right so he could be seen to have solved it where all others had failed. So, armed with a spectrum analyser I drove 500 miles up to Aberdeen in the same model car.

The plan was to log its internal computer module communication network signals while going along the same route and to measure the magnitude of the EMI that was coming from the
tower. Up I went, staying the night in Aberdeen and starting the next day.

Having contacted the local police to explain that I was measuring the radar, not trying to interfere with it (I had visions of being bundled into the back of a police van while being 'helped' by officers with MP5 machine pistols and heavy boots poised for a kicking, looking for terrorists trying to bring down airliners) I fired up the analyser and looked in amazement at the frigging peaks of radar energy zipping up and down the measurement scale as the dish swept on its constant circular scan. That's plenty of interference right there, in fact I'm surprised my eyeballs haven't clouded up from getting that much microwaving just standing there.

A quick word with the farmer whose house was just at the end of a track some 50 yards further on confirmed- oh yes he said, the TV's always buggered, remote control cars zip across the room without being controlled, mobile phone signal is ruined etc. and it turned out that once I got back and checked with the radio regulation rules from Ofcom, the levels actually exceeded what you should be exposing people to.

I did consider ringing up NATS and saying, in an offhand way, you might want to turn that down a bit, but the odds of them kowtowing to my request was minimal - NATS have data sharing responsibility
with the MOD and having a radar looking out over the North sea was considered quite a good idea from a point of view of those regular incursions that Russian bombers make into our airspace just to test the water. MOD 1, RWH 0.

Despite all this, I could not reproduce the fault with an identical car to the one that was supposedly giving the punter all this trouble. No cut out, no anomalous data on the in-car network systems. Nothing. Nada. Zip.

Then out of the blue, after a quick look at what the guy did for a living, it turns out his company supplied marine safety beacons with a satellite uplink (INMARSAT I think) and after a chat it turned out he would regularly carry them in the boot of his car. The bloody things were becoming active after a jolt on that corner (which he must have been taking rather quickly) and from INSIDE the car blasting out several watts of RF energy - supposedly destined for a satellite 60,000 miles up in space, which instead was going up the nearest cable loom and confuddling the f*ck out of the car's internal systems.

Buy-back avoided, problem set to rest, tempers calmed and clashing with the civilian aviation authority unneccessary. However I was utterly and completely shagged out by doing a 1000 mile round trip in under 36 hours. Never again.
(, Tue 18 Oct 2011, 11:56, 11 replies)
for doing a considerable amount of genuine detective work.
(, Tue 18 Oct 2011, 12:28, closed)
^Oh very much this
A click for you...
(, Tue 18 Oct 2011, 16:43, closed)
Motherfucking SCIENCE
For the win!
(, Tue 18 Oct 2011, 12:42, closed)
mother fucking science indeed
Well done that man.
(, Tue 18 Oct 2011, 19:15, closed)
Bloody hell squire Top detecting
I probabaly would have chalked it upto Ghosts and left it at that!
(, Tue 18 Oct 2011, 12:47, closed)
Tis witchery!
(, Wed 19 Oct 2011, 15:16, closed)
I log in to find the top 4 entries are all worth reading and clicking
must be a record.
(, Tue 18 Oct 2011, 14:48, closed)
would it help if I explained that the vehicle was a Honda Accord
and that I was on massive drugs at the time with my supermodel girlfriend?
(, Tue 18 Oct 2011, 15:21, closed)
how do you view the top entries?
there doesn't seem to be a popular page for QotW
(, Wed 19 Oct 2011, 13:40, closed)

Also: bloody hell dude, that was even more convoluted than when you first told me about it! O_o
(, Tue 18 Oct 2011, 15:04, closed)
I don't believe a word of it.
In fact, I heard the exact same story from a bloke down the pub.

But well told, so have a click.
(, Tue 18 Oct 2011, 15:51, closed)
I have to say in RWH's defence...
...that when he first told me the story he showed me all the documentation from his then employers. Seems a lot of trouble to go to, getting fake company logo'd paperwork and everything, just to pass off an urban myth as his own
(, Tue 18 Oct 2011, 16:27, closed)
How rude!
In fact I still have the powerpoint I knocked up after the trip with the location details and the spectrum analyser screen, so

here's some of it

Whoever you know down the pub has no bearing on what I did on that weekend, unless that person was me of course... EDIT if it was someone with the initials DK or RH or MG then they were in my department and have stolen the story....
(, Tue 18 Oct 2011, 18:25, closed)
*claps and clicks*
Well done!
(, Tue 18 Oct 2011, 16:06, closed)
Gets my vote.

(, Tue 18 Oct 2011, 17:01, closed)
...is this week's winner.

I salute you sir.
(, Wed 19 Oct 2011, 9:21, closed)

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