RE: Dead FM Broadcasting Technologies

[Larry Weil <kc1ih@mac.com>]

At 03:37 PM 11/29/02 -0500, Garrett Wollman wrote:

>Can one of you readers who are please explain what is meant by
>``pre-emphasis'' and why it's measured in units of time?  (For extra
>credit, can you explain why said units of time are invariably
>represented with the wrong symbol?)

OK, I'll give it a stab. <ouch>  The whole thing is a way to reduce audio 
noise in FM reception.  Since most of the noise is in the treble range, the 
noise can be reduced by reducing the treble response of the receiver.  Of 
course, this also reduces the treble in the program material, so to 
compensate the treble response is increased at the transmitter by exactly 
the same amount that it is reduced in the receiver.  The result is flat 
audio response, but reduced noise.

This is all accomplished very easily, a single resistor and a single 
capacitor are all that's required (double that for stereo).  It is 
expressed as a time period because that's the time constant of the 
resistor/capacitor combination used.

I'll let someone else deal with the definition of time constant.

--
Larry Weil
Lake Wobegone, NH