Topband: FT-8 performance

[Richard (Rick) Karlquist]

On 8/1/2019 1:27 PM, James Wolf wrote:
> I think there is some misunderstanding of bandwidth using FT-8.

The power limited Shannon limit I posted about today is
independent of equivalent noise bandwidth
>   
> 
> 
> The equivalent noise bandwidth of an FT8 detected tone is only 6.25 Hz.  So

-26 dB S/N ratio in a 2500 Hz bandwidth is 0 dB in a 6.25 Hz bandwidth. 
Thus using the conventional version* of the Shannon limit, the
maximum theoretical bit rate is 6.25 bits/second.  FT8 supposedly can
do about this rate at -24 dB S/N in 2500 Hz.  IOW, it is within 2 dB
of the Shannon limit.

This is all self consistent.

*At a SNR of 0 dB (Signal power = Noise power) the Capacity in bits/s is 
equal to the bandwidth in hertz, according to Wikipedia.

Rick N6RK

> 
> Jim Wolf,  KR9U
>