Its not nearly as much the 3 db having much of a SNR improvement which
Chen has noted, but the major difference is in "presence" on the band
which you can't really quantify. In fact I find with 150 watts if I
act like I am loud stations respond that way.
But much better to spend the money on antennas than on amp's.
Jay
On Wed, Feb 16, 2011 at 10:25 AM, Kok Chen <chen@mac.com> wrote:
> 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
>
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