How to Hook Up iPhone X to Older Cars without Bluetooth or Aux?
There are different ways to connect music player to your car stereo. Some of the common methods are auxiliary input, cassette adapter, USB input, FM transmitter and Bluetooth transmitter.
But keep in mind... you're more or less travelling in a partial Faraday Cage. Where's your antenna? Where's the FM transmitter? Chances are, the answer to the latter is "somewhere near a DC outlet". So if you have one of those in-windshield FM dipole antennas, you might have a pretty good signal, though the direct path to your antenna might be through your dashboard. But if your antenna is one of those shark fins on the roof, you have a 5-10 millimeters of steel between your transmitter and your receiver. So you're already sketchy.
The FM Transmitter is a good idea in theory. The problem is, these things are very low power, as mandated by the FCC or your local equivalent. In the USA, the rule requires an ERP of 0.01 µW, or 10 nW, or -30dBm. So ok, you're only going a meter or so, so that signal at the car's antenna should be around -40dBm to -45dBm, depending on the actual distance. And a typical consumer FM receiver should be good to -90dB or so receive sensitivity.
Then consider that in many areas, the FM band is pretty crowded. You may think you have a clear channel, and maybe you do. Or maybe there's a distant station coming in and out that you never expected. And being low-tech analog radio, it's not as if you get one or the other, you get both.
If wiring (or radioing) in your smartphone or MP3 player is the main goal, Gizmo Guy Gadget will get the job done in the least annoying way possible. It's a cheap thing to try out before spending real money on a new in-dash unit.There is a golden rule in audio which is "you audio quality is only as good as your worst component." If you have a speaker system that isn't especially great, no matter good the quality of the audio going into it, it will never sound fantastic.