Faraday bags a con?

Yes, even the Dartford Tunnel has that.

Exactly. And remember to turn it on before removing it, and its RF signal will be completely undetectable after that.

It for sure does not.,

I lost VHF radio through it last time I used it

This was for my credit cards, not a key fob.

Well your radio is f***ed or you're using it wrong.

FM BBC Nationals, BBC Kent and Classic FM are received from Wrotham; BBC London and Greatest Hits (London) are received from Crystal Palace; Capital FM, Magic FM and Heart London are received from Croydon; BBC Essex is received from Benfleet.

MF: Radio 5 and TalkSport are received from Brookmans Park

There's even a sign telling you that information/safety messages are broadcast on AM/FM at the tunnel entrance. They get inserted over the stations being rebroadcast on the leaky feeder.

That was, I think, where the first leaky feeder trials took place.

Microwave ovens are well shielded at around 2.4GHz but not so well at other frequencies. I just tried putting my DECT phone which operates at about 1.9GHz in the microwave oven, closing the door and calling it. It rang. The door seals rely on using a quarter-wave overlap between the door and the main body to transform an open circuit into a short circuit, but only at the intended frequency range.

John

Indeed my phone rings when called if its in there, local GSM site operates at 860 odd MHz...

I wouldn't count on it. At those frequencies RF signals can squeeze through the tiniest of cracks and gaps.

No, they cant

Some cars, eg Toyotas, have keyless door locks. The fobs emit a broadcast the car detects.

They detect the fob in your pocket / handbag etc as you near the car and unlock it when you touch the handle.

By ‘relaying’ the signal from the fob sitting in your house to your drive, they make the car ‘think’ a fob is near….

I assume a similar process works to start it.

On Toyotas, you can inhibit the ‘broadcast’ very easily. This also saves fob battery life.

Same principle, try to pay for an item, contactless, with the card covered..

Though that has the same issue as I had with the car. If the screening is marginal, it might block one reader but not another slightly higher-powered one!

nib

The card process is more complex. The card is powered by the wireless signal from the reader, and transmits back to the reader. The transmit power from the card is fixed, so no matter how "powerfull" the reader is, you still get the same signal from the card.

Dave

Is the power the card can emit fixed, independent of how much power it receives from the terminal?

nib

Provided it gets enough power yes. Getting the things to actually work as designed is a challenge. Stopping them working is easier...

Dave

What about some terminals being more sensitive to the signal from the card?

nib