today, with minor exceptions, am stations retain the two letters after the numeral, and since 1975 fm stations have had three letters. over the last few decades, there has been a trend for many stations to use "marketing names" on air rather than their official call sign. inter alia, examples of such on-air names are: gold, mix, hotfm, nova, and star fm. stations will often change their marketing name even when there is just a small change in format.