Pledging Allegiance to Public TV: KCET Channel 28 reported that its August fund-raising drive was its best ever. The station received $1,009,432 in pledges, which was 6% more than last summer's total. The average pledge of $70.57 also set a record for the station--last year's average was $57.39. Pledges came in from 14,304 viewers. . . . Public television nationwide set a record during the August pledge period--PBS received $14.2 million in pledges, which was 31% over last year's total, according to preliminary reports from 73 stations.