More and more people who receive television signals over the air -- rather than by cable or satellite -- are aware that they will not be able to do so come September without purchasing a converter box, but relatively few of them have done so, according to a new survey by the Association of Public Television Stations and reported on the Broadcast Engineering website. The study found that 70 percent of over-the-air households said they know that they need to purchase a converter and that 8.8 million said they would do so. Of those requesting government-issued coupons to cover most of the purchase price of the converters, only 54.2 percent said they had redeemed them, and of that group just 38 percent have installed the converters. Only 12 percent of the over-the-air households said they would sign up for cable or satellite.