[RTTY] What should I expect from 3db improvement in SNR?

[Kok Chen]

On Feb 16, 2011, at 2/16    8:05 AM, N2WQ wrote:

> So, recognizing that I have a few other improvements to make, what  
> should I expect from extra 3db SNR on RTTY?

It will depend on band conditions.

Again, take a look at Alex VE3NEA's measurements here:

http://www.dxatlas.com/RttyCompare/

The first plot for AWGN represents perfect band conditions in the  
presence of only noise.  Look at the horizontal axis.  Notice that a 3  
dB change can take you from good copy (3% character error rate) to  
gibberish (30% character error rate).

So, 3 dB better SNR will take you from a useless signal to one that  
prints much better than you would need in a contest that allows you to  
repeat an exchange.

Now scroll down to the Selective Fading plot.

Notice that it now takes about 13 dB to cross this decoding  
threshold.  So, a 3 dB bump in the SNR is not very useful.  3 dB  
improvement can get you from gibberish to ...umm... less gibberish :-).

73
Chen, W7AY