What does your car radio sometimes lose signal when you come to a stop sign or stoplight, then comes in clear again when you roll forwards a few inches/feet?

Question

see above

In: Engineering

Answer 1

It’s due to “multipath interference”. On its way to your radio antenna, a radio wave can also bounce off various things (buildings, trees, cars, etc.). The reflected versions of these multiple paths take a little longer to get to your antenna than the most direct one, so they are out of phase with the original. (The peaks and troughs don’t line up.) This can cause destructive interference to occur, degrading the radio signal. (It can also result in *constructive* interference.)

If you move your car just a little bit, you change which reflections are hitting your antenna, and the destructive interference can be increased or reduced.