UPDATE 1-Speculators raise net-short dollar bets to $7.81 bln -CFTC, Reuters

(Adds details on data, analyst quote, tables) Dec 15 (Reuters) - Speculators raised their net-short bets on the U.S. dollar to $7.81 billion in the latest week, the 22nd straight week of bearish bets against the U.S. currency, according to data from the Commodity Futures Trading Commision calculated by Reuters. It was the fourth straight week the net-negative positioning on the dollar has increased and was the largest net-negative position since Oct. 24. The bearish bets almost doubled