RF ID cards

[mleanz]

Hi Guys,

I'm new to this forum and also new to electronics and was looking for some advice.

I'm in the UK and my university has issued us all with new ID cards. I have no problem with having my ID card on me at all times. However the new cards are all RF and according to my tutor the university are monitoring where we go (he's brought a shield for his card). I want to build a jammer to jam the signal when I walk through doors. I've spoken to members of staff (all of whom are against the new system) and they have told me to do it. I have no idea where I would get the parts and what I'd need!

Any suggestions? Many thanks,

Mark

P.S I know this may seem a bit crazy but I'd also enjoy actually making a jammer as I've never done anything like this before.

 

[OLIVE2222]

Hi, you ID cards are probably RFID types. You can't really do tracking with such cards.
The maximum reading distance (for the UHF ones) are few tens of meters. What they can do is tracking you when you enter or leave a premises thanks to gates containing a reader.
They can have a precision according to the amount of gates they deploy.
Regarding the jamming you need to know which frequency band is used then you must transmit on the same frequency. You can have a idea of what to do by googling GSM jammer. Of course occupying a part of the RF spectrum whithout licence is forbiden and even dangerous, think about jamming airband frequencies, emergency frequencies, fireman frequencies ...

Olivier

 

[davelectronic]

Hi mleanz.
I found this if its of any use.
It seems like retail security type RF tracking.
Link below.
The site is a bit of fun full of hacked modded gadgets, i am a member, it safe site.
Dave.

http://www.instructables.com/id/How-to-blockkill-RFID-chips/

 

[mleanz]

Thanks guys!

And my tutor told me its 144mhz

 

[mleanz]

From what i understand i need to build something that transmits at that frequency. Where would i be able to buy such items. Ive been looking at maplin! But don't fully understand what i need!

 

[OLIVE2222]

144Mhz is reserved for HAM, you probably got a wrong information here.

Actual used frequency for RFID (assuming that's what they use) are:

~130Khz, almost "contact" reading
~13.56Mhz around 10Cm reading
~870 MHz the UHF ones few tens of meters reading

before buying anything you must grab information's, what's look like as the readers, any logo, any brand? can you do pictures....

This is what a frequency allocations (US)looks like:

http://upload.wikimedia.org/wikiped...locations_Chart_2003_-_The_Radio_Spectrum.jpg

Believe me the system we talk about must use an allowed frequency !

Olivier

 

[mleanz]

ahhh ok then!
Well another tutor said it was 125mhz but he's not as reliable, Is that a possiblity?

 

[OLIVE2222]

No, the 3 possibilities are listed in my previous post.

 

[davelectronic]

I know a way you might be able to find out, i have a scanner i listen to the vhf and amateur bands, but my alinco can find bugs and pick up frequency's in all common modes, and almost any frequency, dont know if you have one or can borrow one, there expensive, i got mine in a swap it was damaged, but repaired it with a replacement board, still cheap, retail £ 280.
Dave.

 

[davenn]

well the most obvious jamming method and almost totally free is to wrap a bit of aluminium foil around the card. it will totally block its use
it would be real easy to make a foil lined pouch that the card could be slidden in and out of for needed use

Dave

 

[(*steve*)]

If you have to place the card against the reader (or very close to it) to have it work normally then it's 125kHz.

These are pretty common. The cards are almost free these days.