The old ADF in the 707 & 727 were just like tuning an old AM radio. You would place the frequency under the lubber line and then move back and forth until you got the best signal. If there was a lot of noise and the signal was weak you could turn on the BFO and that would help you tune to the station. Of course, you would always ID the station using Morse code. The later planes had digital tuning in the ADF - that took the fun out of getting on frequency. You could use any AM station as well as aviation stations in the ADF. The only problem with commercial stations was that they only identified themselves every so often.

Lou