Ben Fong-Torres, in his radio column in today’s Chronicle, says KGO-AM 810 has been booted from the No. 1 spot in the market among all listeners in January by all-news KCBS. As he notes, KGO’s Mickey Luckoff says a survey for just one month is a small sample, and there are a lot of questions about Arbitron’s switch to personal people meters. Besides, advertisers don’t buy time based on cumulative ratings but on how a station does in a particular demographic. But KCBS came out on top in the morning drive among listeners 25-54, while KGO was 12th. One reason for KCBS’ advance is that it now is heard on both AM (740) and FM (106.9). Which raises the question, when will KGO add an FM signal?