2011-11-22

Fox Hunting on 403MHz

Its in the news again! Thieves are jamming the car security remotes, so you can't lock your car/garage/gate.

The jamming of the car remotes by the 'bad guys' is going on all the time in South Africa. Mostly at busy shopping malls. These car thieves are well organised with medium power jamming devices.  Which should be easily detected by Doppler or RDF receivers. It doesn't matter how 'secure' the code is, these 'jammers' work by blocking the receiver from getting the code to lock the car doors.

Having had some personal experience in this field as well as the previous ZS6WL, it would be simple to make a 403MHz receiver.

How about 'we' as a club, make a project that serves the community by detecting these thieves. As Radio Amateurs 'we' could use our experience in 'Fox Hunting' and assist the police and security firms in catching these crooks.

In the late 80's an 'incident' was recounted to me by Anti-Car-Rob. They were in the process of developing a local car security system. All the previous versions were of Italian manufacture and imported illegally as they did not comply with local radio regulations.

They also had a minimal set of codes. Most cases this was less than 4096 possibilities. A 'person' who had an axe to grind went around all the car installers with a small coded transmitter. The transmitter went through all the codes in about 3 minutes, opening all the car's doors on the lot! He went round all of them in a matter of a few days. I believe he convinced most to sign with his 'new and improved' security system.

Later on these 8 bit coded systems were recorded and 'played back' to the systems. Thus opening the cars, gates and garages.

While (my long time friend) John Whitfield was working at M.S.I., he introduced both a 'frequency hopping' system and a pseudo random sequence code. Also he produced and got approval from ICASA for a super-heterodyne design working on 403MHz. This had better 'selectivity' thereby could be immune to 'blocking' than any of the previous receivers. Most current (approved) systems work on this frequency at low power (milliwatts).

On the 'down side' of this, it appears that most insurance companies will repudiate claims of theft. Especially when the car has not been broken into.
So make sure that your car/garage/gate is locked when you press your remote.

I got a very quick response from my friend...

I always walk 10 metres away and relock the car. Always have done and always will. The Crooks will think they got you first time so be surprised at the second lock and not catch you.

Best regards
Peter Greaves

The remote transmitter in your hand is very low power (milliWatts) and the interfering transmitter may be medium power (Watts). The chances of you getting your signal through, 10 metres further away from the receiver are not in your favour!

Rather make sure when you are close to the car.

No comments:

Post a Comment