Better than any short-range FM transmitter, you can get a hardwired Bluetooth FM modulator that plugs directly into the antenna port in the back of the radio head unit, then your stock antenna cable plugs into the modulator. The modulator picks up your Bluetooth and taps the output signal directly into the physical antenna circuit at one of (usually) two selectable frequencies on the radio dial; here's an eBay search for them . There's also similar, older-style FM modulators without Bluetooth, just an aux-in jack; these were commonly used to tap aftermarket CD changers into stock factory radios back in the day. IMO these would be preferable if your audio source (e.g. phone) has an aux-out/line-out or headphone jack. Anywhere you can eliminate a wireless signal in favor of a hardwired connection for audio, the better. Finally, if your stock head unit has a cassette player, there's also rechargeable dummy cassettes with Bluetooth built-in, so your phone would transmit a BT signal to the cassette adapter, which would then feed the audio signal right into the tape head just like playing a real cassette tape. More on reddit.com

I think the best option here is to actually fix the cigarette lighter. Almost all of theses have an attached fuse that is worn out over time, called a fusible link. So just buy a new port, they are not hard to install. Two problems fixed at once. What kind of car do you have? More on reddit.com

Lmao, no. The interference will still be there. Unless you get one that has been set up for more broadcast power. If your car has a cassette player, use one of those cassette to 3.5 mm aux adapters, or if your car has a normal 1 din or 2 din radio slot you should be able to buy and install an aftermarket radio. I know the used ones go for hella cheap over here. Good luck More on reddit.com

The adapters are DC-DC switching power supplies. They turn the 12v of the car into 5v for your USB plug by rapidly switching between on/off to regulate the voltage. This switching frequency causes a lot of interference that is spewed out because the plastic case can't contain it properly. It goes away when you unplug it because it switches off and stays off. To stop it, you'd have to shield the wiring or rewire it completely into a new shielded case. If your car has rear 12v plugs, you could try that. Moving it away from the antenna/radio would help. More on reddit.com