olin1963
Any antenna that is small enough to fit on a moving vehicle will be less than ideal for the AM radio band. Most mobile radio antennas are actually cut to a length of around 30 inches to match the FM radio band. An equivalent antenna to match the AM band would be approximately 224 feet long. However, many AM car radios do have a tuning adjustment to compensate for AM antenna length. This is sometimes accessible from a hole in the front of the radio so it can be adjusted without removing the radio. Ask a car audio tech for help in optimizing this adjustment. WK