Modulation, RF and security

OK, sorry about the lack on information.  What i'm trying to do is get
access to the data being sent from a transmission from a 868 burglar
alarm for some testing on the security of the system wrt jamming,
interference etc.  Obviously the first step is to gain access to the
actual data.

The transmissions are short pulses, persumably containing a short data
sequence, maybe a few bytes.

My initial thoughts were to 'grab' a sample transmission using a RF
signal analyser from national instruments that can downconvert and
demodulate the signal for me.  However, the hardware for this is just
shy of �20k, but allows the flexibility of demodulating virtually any
signal, from mobile phones, bluetooth etc.

If I knew more about the signal, then it may be possible buy a less
flexible solution, but cheaper.

Anyone got any experience of this?


Thanks

sam

samsspam@btinternet.com (sam) wrote in message news:<ba2c2b89.0311190306.67019b4a@posting.google.com>...
> OK, sorry about the lack on information.  What i'm trying to do is get
> access to the data being sent from a transmission from a 868 burglar
> alarm for some testing on the security of the system wrt jamming,
> interference etc.  Obviously the first step is to gain access to the
> actual data.
> 
> The transmissions are short pulses, persumably containing a short data
> sequence, maybe a few bytes.
> 
> My initial thoughts were to 'grab' a sample transmission using a RF
> signal analyser from national instruments that can downconvert and
> demodulate the signal for me.  However, the hardware for this is just
> shy of &#4294967295;20k, but allows the flexibility of demodulating virtually any
> signal, from mobile phones, bluetooth etc.
> 
> If I knew more about the signal, then it may be possible buy a less
> flexible solution, but cheaper.
> 
> Anyone got any experience of this?
> 
> 
> Thanks
> 
> sam

Quick-and-dirty?  Use an AM radio to capture and demodulate some 
harmonic of the signal.  Interfering station?  Use a second AM 
radio as a BFO.  What's a BFO?  Never mind...

Regards,
Ken Asbury

sam wrote:

> OK, sorry about the lack on information.  What i'm trying to do is get
> access to the data being sent from a transmission from a 868 burglar
> alarm for some testing on the security of the system wrt jamming,
> interference etc.  Obviously the first step is to gain access to the
> actual data.

Well, you should always assume that the enemy has all the information 
about how the system works, so you should have that, too.

You mean the KD-868?  (results of a quick Google search.)

> The transmissions are short pulses, persumably containing a short data
> sequence, maybe a few bytes.

If it is what I think it is, the transmitters have to be pretty cheap. 
There are transmitter ICs commonly used for garage door openers.  I 
believe they are digital on/off modulated, with a carrier somewhere in 
the 900 MHz range.

> My initial thoughts were to 'grab' a sample transmission using a RF
> signal analyser from national instruments that can downconvert and
> demodulate the signal for me.  However, the hardware for this is just
> shy of �20k, but allows the flexibility of demodulating virtually any
> signal, from mobile phones, bluetooth etc.

> If I knew more about the signal, then it may be possible buy a less
> flexible solution, but cheaper.

> Anyone got any experience of this?

Buy one of the transmitters and take it apart.  It won't take long to 
figure out the modulation or the carrier frequency.  (Unless it isn't 
what I think it is.)

http://www.itm.com.tw/5kendu/wireless-burglar-alarm-manufacturers.html

-- glen