FM broadcast stations use pre-emphasis to increase the deviation
of high frequencies, boosting those above 2kHz-ish (North America)
and 3kHz-ish (EU/AUS). The time-constant is like the inverse of
that corner frequency. In the receiver, you have to reverse the
process, to get back to a flat frequency response.
Think of it like progressive treble boost on transmit, then
treble reduction on receive. It's all about getting best signal
to noise ratio. Similar processes are using on vinyle records
Whether to select 75 or 50 depends entirely on what the WBFM
stations you are receiving as using, so 75 should be good for your
Try swapping it while listening to a high-quality classical music
channel and you might hear the difference. Speech and compressed
electronic music might not form the best test signal for
On 22/06/2019 18:51, robert ross wrote:
WHAT EXACTLY IS…"Demod Settings, De-emphasys time
constant” ?? I see mine was set to 50us, so I changed it to
75us as you suggest. What does that actually do?? Is this
gonna work even better now that I have changed it to 75us??
Why is it different for USA and the World. I assume CANADA is
the same as USA…since I am in CANADA.
for any insight on this Demod Settings,
De-emphasys time constant adjustment.
On Jun 22, 2019, at 13:12, Bill Nollman <billct97@...
If you are in the
US you also need to set the WBFM de-emphasys for the
Settings, De-emphasys time constant – set the
dropdown to 75us for the US, 50us for the rest of
the world, OK.