Sam: I swear that WDAS (AM) did not go on the air on 1480 from the stand-alone studio building/transmitter site it still uses until the summer of 1955. I went to college in Troy NY and that summer, I was a co-op student working at the old General Electric switchgear works at 6901 Elmwood Ave in southwest Philadelphia. I lived around the corner at 7022 Paschal Ave. WDAS had, for many years, been a Class IV station (graveyarder) on--I believe--1400. In those days, graveyarders were limited to 250W-U. The move to 1480 with 5 kW-U/1 kW-N DA-2 meant a big increase in the daytime signal where I was living, but the night signal, which had been pretty much unlistenable on 1400, totally disappeared when the station moved to 1480. If you look at the directional pattern, you will understand why. The four tower night array produces a relatively narrow teardrop pattern beaming southeast that protects stations in Fall River MA, New York City, Richmond VA. and Canton OH, among others. The night signal must be quite strong in the northern parts of Philly and probably even in Center City but not in southwest Philly.
As for when WTEL moved to E Norriton and 860, breaking up the time-share with WHAT, I think that probably took place in the early '60s--not the early '50s as you reported. I believe that WHAT and WTEL were still sharing time on 1340 during my summer in southwest Philadelphia. It was a miserably hot summer and I like to tell people that I spent the worst ten years of my life in Philadelphia during the summer of 1955;>( It sure FELT like ten years.