Does anybody have a circuit which will allow me to detect the strength or presence of a key FOB signal. If I repair one, I would like to be able to test it afterwards. This would be in Canada if that is of any consequence.
Thanks in advance.

 

FOB????
http://www.urbandictionary.com/define.php?term=Fob

 

FOB????
http://www.urbandictionary.com/define.php?term=Fob

Cute.
Now google key fob.

 

Try an RF probe. http://rookieelectronics.com/sensor-rf-radiation-detector/

 

Try an RF probe. http://rookieelectronics.com/sensor-rf-radiation-detector/

An RF key fob could well be somewhere in the general direction of 2.4GHz - yer average 1N4148 might not cut it.

Probably needs to be Shottky - but some of those are more RF than others.

 

This may save you sometime. Our VIP/O'Reilly Auto Parts has one on their counter. It is for customers to use, but you may be able to get a manufacture and/or model number from that.

 

There are several out in the marketplace and that would be easy to do, but I am looking to build one and I figured someone on here in all their wisdom and libraries, might just have a drawing around. Barring that, I may just buy one and reverse engineer I guess.

 

they are usually in the 433 MHz range, a germanium diode across your meter probes should read a few millivolts.

 

There are several out in the marketplace and that would be easy to do, but I am looking to build one and I figured someone on here in all their wisdom and libraries, might just have a drawing around. Barring that, I may just buy one and reverse engineer I guess.

Some years ago Elektor published a simple circuit for a cell phone sniffer, the basic idea could probably be adapted for whatever frequency the key fob uses.

If the key fob uses 2.45GHz - you could try pointing it at a microwave oven leakage tester just to see whether anything happens.

 

Is there a device or circuit which can tell you exactly what frequency something is transmitting at?

 

Please watch where this is going... Cause this could go towards stealing cars or illegal activity...

Thanks
Jay Sr

 

Please watch where this is going... Cause this could go towards stealing cars or illegal activity...

Thanks
Jay Sr

Really? How would that work? the operational frequencies of key fob transmitters is not a secret nor is it any use to a car thief.

 

Please watch where this is going... Cause this could go towards stealing cars or illegal activity...

Thanks
Jay Sr

Most car key fobs use a rolling code - knowing the RF carrier frequency won't help you much.

 

Really? How would that work? the operational frequencies of key fob transmitters is not a secret nor is it any use to a car thief.

Lol I am Repo Man .. There are alot of cars that use it instead of locks ...

 

Lol I am Repo Man .. There are alot of cars that use it instead of locks ...

Use what instead of locks?

 

Use what instead of locks?

Merc cars come with a fob remote that is used to open a car and start them .. Most cars have a sensor close to the ignition but not part of ignition so if you can break the lock cylinder and send the key code to the sensor then you have working car.. Also how do you think auto start remotes work with a ket fob car or truck...

 

Merc cars come with a fob remote that is used to open a car and start them .. Most cars have a sensor close to the ignition but not part of ignition so if you can break the lock cylinder and send the key code to the sensor then you have working car.. Also how do you think auto start remotes work with a ket fob car or truck...

I understand how car security systems work. My question to you is; how does knowing the carrier frequency of the remote control key fob assist anyone in stealing a car?

Furthermore, the sensor mounted around the ignition barrel is a close proximity transponder reader that energises and reads a chip in the key and has nothing to do with the active transmitter part that controls the central locking and alarm.

 

Merc cars come with a fob remote that is used to open a car and start them .. Most cars have a sensor close to the ignition but not part of ignition so if you can break the lock cylinder and send the key code to the sensor then you have working car.. Also how do you think auto start remotes work with a ket fob car or truck...

I have to say I'm with blocco on this one. You are confusing two different systems with each other. Chipped keys were an early design security system that started out with different resistor chips in the key. If the resistance wasn't proper, car would not engage starter. Key FOB's today have a rolling code which changes after every initialization of any button on the FOB and is nearly impossible to duplicate. That is why I know I can ask my question and not break any rules. With over one trillion possible combinations, it would be very hard to guess the right code. I just wanted to find out the frequency of some of my FOB's so I could build a device which tells me if I am sending a signal from a repaired FOB

 

You say impossible and I say already done..
Check it out
http://www.kpho.com/story/22176874/new-auto-theft-device

 

You say impossible and I say already done..
Check it out
http://www.kpho.com/story/22176874/new-auto-theft-device

It is impossible to say what is happening here from the limited information given. The vehicle remote controls may have been cloned, we don't know. I guarantee that what the thieves are not doing is transmitting an unmodulated carrier to open the doors.