There has been some confusion (mainly on my part) about the hidden feature behind button number 5.
Pressing and holding the number 5 will toggle the radio between 50 and 75 uS.
But what, exactly, is this function?
Thankfully, Eric Cottrell has the answer:
“The 50/75 uS setting is the FM De-emphasis. 75 uS in the US and 50 uS in Europe.”
Eric then pointed to a discussion about de-emphasis on DIY Audio’s website.
Many thanks, Eric, for clarifying this (and thanks to others SWLing Post readers who pointed this out in comments as well).