Thread: Problem with using a mobile in the Disco 2

I work at a Dealer and I have never heard of it .

G'Day Ian

I am a radio interference engineer & your story does not surprise me. You are right, cars are supposed to be interference proof by law but some things can slip through the cracks.

Each case is different, but one thing to consider could be a car kit for the phone that has an external antenna. Put the antenna on the roof, where it does not have a clear path into the cabin. Ditto for any 2 way radios you have.

The likely coupling path for interference from a transmitter (mobile phone) to the security system is via sensor wires that may go to motion sensors, door switches etc (don't know the Disco too well at this stage) - the wire literally act like antennas to receive the phone signal and route it to the security system, possibly stopping it. If you are talking on a mobile in the cabin, you & the phone may be quite close to some of the wires, so coupling could be pretty good.

The possibility of interference with ABS, traction control, engine management, etc is very real, and the fact that LR have put something in the book suggests they may know of a weakness. The security system was probably deemed low risk (compare to ABS failure for example) & maybe this is why they didn't add extra filters or shields.

Hope this helps.

Originally Posted by pk.hoarder

I am a radio interference engineer & your story does not surprise me. You are right, cars are supposed to be interference proof by law but some things can slip through the cracks.

Not wanting to start a war or argue too much about this (your qualification/skill set description makes that dangerous), but nowhere does any Australian law or standard state any electronic item must be immune to electrical noise or interference.

The standards are biased heavily towards the emmissions (what gets out electrically) rather than being immune to what might get in.

In a Disco owners manual this is what it states, I think it is called covering one's backside.
"NEVER operate a mobile phone fitted with its own aerial inside the vehicle - the electromagnetic field radiated by the phone may interfere with the vehicle’s electrical systems."

The Freelander is obviously a 'hardened' bit of kit, probably to Military spec, it must be because 'never' has been replaced by 'refrain'.
"Refrain from operating a mobile phone fitted with its own aerial inside the vehicle"


Your description of the various inherant antenna fitted to the cars wiring is spot on, if it conducts and is connected to other bits it can suck up lovely bits of radio signal.

SuperMono and pk.hoarder, you guys are obviously articulate and educated

True; The D2 Owners Handbook does warn the owner against using the mobile.

However, who hasnt turned on their mobile when your QANTAS flight is landing, just to see if the 737 spiralls into the ground.

And who has had a phone call on their mobile when filling up the LR with (a lot of) fuel and exploded!

Cautionary but only through the worry if prosecution by LR is my un-educated input here.

Your GPS will be Ok to operate inside the car. It's only a receiver not a transmitter. And the laptop if you turn off any Wi-Fi and possibly Bluetooth.

As for the phone, sounds like it's been put there to cover themselves for any liability. ( like the "may contain traces of nuts" message on every packet of food you buy these days. )

Mobile phones are quite low power I don't really think you'd have an issue. If possible, use it with a car kit and external antenna, that way you're putting any radiation outside the car not inside.

Aside from agreeing that the chance of all or any system suddenly turning hard left into a tree is very low, a quick note about electrical noise.
It doesn't have to be a radio transmitter to be the source of radio like emmissions. Anything with a (modern) power supply or a CPU (which is basically everything now) can cause Radio Frequency Interference (RFI).

simonl8353, as I spend a fair bit of time aboad things with QANTAS written on them, can you post your airtravel plans when you make bookings please, I would like to ensure I don't share your test program on a 737