Quote Originally Posted by retired99 View Post
If the cradle is connected to the car's aerial could the signal be transferred from the cradle to the phone by induction?
YES! I have an old HP Palm Pre 3 that has the inductive charger 'touchstone' thingy that you stick on your desk and the phone attaches to it magnetically and charges without being plugged in. At home the T-mobile / EE signal is weak at best (although it finds 3G where my work phone on Vodafone does not).

Anyway, phone off touchstone I have to wander around the house to find enough signal to send / receive SMS. When it sits in the touchstone I get 2 or 3 bars. There is no antenna functionality on the touchstone so patently the phone is ("unconsciously") using the touchstone as an antenna... and probably the USB power cable attaching to the wall wart power brick.
Actually this is not as weird as it sounds... many mobile phones that offer an FM receiver capability require the headset to be plugged in as they use that as an antenna. I'm pretty sure it is a more intentional use of the headset as an antenna rather than an accidental use but the same principles probably apply.
My guess is that the iPhone is simply able to use relayed signals from the car loom to get better reception.