WBAP's QSL card received in 1974.
WBAP on 820 kHz made it through to Pinelands at 0520 UTC on the 17th August 1974 via the Siera valve receiver and 20 metre longwire antenna.
I was fortunate to receive WBAP's QSL card, from Director of Engineering Rupert Bogan on the 3rd September 1974 (In 12 days after posting my reception report).
A close-up of the AM station details.
Google Earth Image of WBAP's omnidirectional transmitter tower.