[guygee]

Originally Posted by jameskg

If you record from the receiver, it should already be de-emphasised, and you wouldn't see much in the analysis to betray the presence of the processing (unless the receiver is a piece of shit). FM transmission has a response of 15kHz on each channel and rolls off sharply after that. That doesn't mean you would see a tone at 16kHz. I don't know where people get that from.

Quite apart from the issues of this recording, I've looked at FAs and SAs of many FM recordings made at the receiver, and it seems this 16 KHz signal (actually just below 16 KHz) is very often present. I've researched this topic, and found specs for modern hi-power FM receivers, and one of the features commonly mentioned is sampling at 32 KHz. Going back into the '70's and '80's I would guess that the technology was different but the effects were nearly the same (using analog filtering instead of digital sampling). Regardless, it seems this signal often survives to make it into a recording made at the receiver. ( A lot of crappy FM receivers? I wouldn't be surprised if that is the case. Or maybe many people have their TVs on while recording...thanks for that interesting angle direwolf.)