Key Fob Jamming

[Hilux2400]

If my understanding is correct the key fob generates a signal at 433.9mhz, but it can be overwhelmed by a signal at the same frequency but of greater magnitude.

 

Most times my key fob works OK, but there is one location in a local supermarket car park when it does not work.  I can lock and unlock the car with the key, but not with the electronic fob.  At first I thought it was a faulty key fob, but when it happened twice in the same location I thought there must be something else going on.

This has also been happening to my son with another make of car when the car is parked on his driveway.  Sometimes his key fob works on the driveway and at other times it does not.  Recently, when staying with him this fault occurred twice.  Mysteriously it stopped just after 10.00 am. After which time there was no re-occurrence of the same problem.

 

My son has since bought a meter which registers and measures an RF signal.  In his area there is a continuous background RF signal about a fifth of the magnitude of the signal put out by his key fob. When the background signal is at this level, the key fob functions as it has a much higher strength signal.  Since buying the meter, the key fob has continued to work, but also there has not been a high overriding background RF signal.

 

It seems that many domestic signals are generated on the 433.9mhz frequency.  They are mainly short burst signals, so normally don't give problems.  Typical examples would be: garage doors, driveway gates, domestic heat controllers or short wave radios.  If these are strong and continuous I believe they could cause problems.   

 

Has anyone had similar key fob problems?

 

H

 

[DBJoe996]

Around your house could be an amateur radio operator or your Ministry of Defence.  The 433 mhz frequency is popular for all sorts of uses. https://en.wikipedia.org/wiki/LPD433

As for the supermarket parking lot - do you notice any remote cameras that may transmit to a security camera system?  They probably transmit in the 433 mhz range.

Edited December 9, 2016 by DBJoe996

[Hilux2400]

I'm OK at my home, but I'll look out for cameras next time I'm at the supermarket. I'll mention the cameras to my son, as he has some new neighbours who might have installed something.

 

Thanks H 

[dporto]

I believe it's called... "The Twilight Zone"...

[Hilux2400]

Nice one!