Car fob RF protection

Equipment
21

I wouldn’t worry so much about the starting - but getting into the car in the first place!

The 433.92MHz (315 MHz in the Americas) frequency is used for locking / unlocking & also disable the engine via the security system. The keyfob is the transmitter while the rx is in the vehicle.

It sends a code unique to your vehicle (which is why losing a key can be expensive). They can be jammed by a strong CW signal - in the early days a strong FM Broadcast signal was enough. I worked at some BBC Transmitter sites and it wasn’t unknown for newer (1990s !) cars to be stuck, dead, in the car park.

The stop start system uses a 125kHz passive proximity system via inductive loop - so if you can get in you should be fine. The active side is in the car, the key is the passive bit.

Modern systems, with improved security, also use an Ultra Wideband signal (in the 4GHz range if memory serves) which exchanges unique data with the keyfob to reduce theft risk. These have been defeated by criminals using relays (RF tx/rx - sot coil & contact !) to intercept and the code exchange.

You may have gathered, I’m now ex-BBC and work in the Motor Trade…

Shave & A Haircut

G4MAD

4 Likes
22

I’m probably the only activator to run more than a few watts of 70cm on a summit! :grinning:

BTW, I don’t recall Paul ever having an issue with his vehicle fob.

Excellent news - this is indeed what I wanted to hear! The fob has a “hidden” key to physically get into the vehicle in case the fob battery dies. My concern was more would the fob be scrambled so that I could not start the car. The manual gives 433MHz as one of the remote control frequencies and the other frequency is decidely LF. Looks like it should be okay and I won’t have to find a stick to thrash the vehicle like Basil did. :grinning:

2 Likes