About 10 years ago I bought a device that you plugged into your portable CD player and it broadcast an FM signal that you picked up through your car radio. I used it for my minidisc player to listen to recordings of my band's jams on the way home.

It was always flaky, not very good quality, but you could usually get it to a point where it worked OK.

I bought a new one today under the completely false assumption that after 10 years they'd be better.

The one I bought (Belkin Tunecast II) is in fact far worse than the ten year old version. The only thing going for it is its digital tuner. Otherwise, it's useless. Unless someone is physically holding the device it simply doesn't work. I presume when being held, the human acts as an aerial.

Do not get one.

I intend to take it back for a refund.

Instead, I intend to spend some money getting a cheap in-car stereo with an Auxiliary plug on the front. It's something I always thought they should have and finally it seems reasonably common.

That can't possibly go wrong.