[RTTY] 300hz or 500hz IF filter?

[Kok Chen]

On Aug 25, 2013, at 2:20 PM, Bill Turner wrote:

> Why would anyone follow a formula that doesn't work in the real world?

I give up, someone explains else explains to Bill how the concept of Bandwidth works.  

If the Butterworth example does not work, I don't know what will convince Bill about the difference between Bandwidth (which is a finite number) and the Frequency Response (which could be unbounded).  I am now convinced that he is mixing up the two concepts.

Bill, the 1.2 number is derived at empircally to get a bandwidth number so that 99% of the power is inside the resultant bandwidth.

If you send a lot of Baudot R or Baudot Y (or Baudot 4 or 6), the bandwidth will probably exceed that 249.45 Hz number by a percent or two.

BTW, if ARRL eventually gets the FCC to pass a bandwidth rule, that ITU number is the only technical argument to allow us to operate steam RTTY inside the "300 Hz" segment of the bands.  Otherwise, we will be stuck with living among Pactor III signals.

73
Chen, W7AY