WAAF was/is one of the first 50 radio stations licensed in the US that still exist (as WNTD). It was too close to WWJ Detroit to be fulltime, even with 500 watts, until directional antennas started becoming more common in the late 1930s to early 1940s. Then, problems with having to have two sites due to the centrally located daytime site, a required complicated multitower directional antenna, a huge North South oriented city spanning nearly 30 miles, and getting a nighttime interference free signal over 80 percent of the city, all while getting a lot of grandfathered interference from WWJ (since the late 1930s a 5000 watt two tower array with just two shallow 1000 watt equivalent nulls toward WPEN and KPRC until the late 1990s), were some of the problems. Also, until sometime in the 1960s, you couldn't increase power at night, and you had to be 1000 or 5000 watts, no more than 5000 watts, and nothing officially in between. All this led to WAAF...WNTD not being authorized fulltime until circa 1980.