In the 1930's there was little in the way of sound recording. Dictation machines were still largely using wax cylinders not too far removed from Edison's early phonographs, and were an item of the upper business executive. Record recording was more of an item of a music recording studio, and used a wax disc or similar, later metalized and used as a transfer master. Film audio recording has only been out since 1927 and was only found in film studios. Magnetic recording was to a steel wire and was a hidden experimental trade secret in Germany. None of these types of recording devices were likely to be co-located with a short-wave receiver.
The most common recording machine of the day was dictation to a secretary or stenographer who wrote in short-hand.
It's amazing that we have Betty's original notebook and that Tighar got to interview her. Although not a stenographer, she represents the major recording device of the era!