Non-Directional Beacons at airports are still in use today , a very early navigation technique that anybody can tune into and hear just below the AM broadcast band . Typically a two or three letter Morse signal identifying the airfield in modulated form is transmitted each 20 seconds or so, after sunset the skip comes in and I have heard NDBs as far away as QLD.
Bill Babb mentioned to me that the Dept. of Civil Aviation (DCA) here had converted many WW2 era BC-191/BC-375 sets into airport NDBs .
https://www.airwaysmuseum.com/Radio%...hill%2050s.htm
Bill came home from WW2 with his kit bag full of radio bits he had salvaged from wrecked aircraft up in PNG and this began a life long interest in military radio gear.
i found his file in the NAA records
https://recordsearch.naa.gov.au/Sear...aspx?B=4844897