On Mon, 25 May 2015 12:40:31 +0100, charles wrote:

If you've got a properly installed aerial, then your "little
transmitter"
is the wrong side of the tin box (known as the car body).

But it will be physically so close to the radio/cassette unit it won't
need to rely on any antenna; it will couple straight through to the
unit's PCB's RF input stage via induction.