[Elecraft] FSK power

[Kok Chen]

On Sep 23, 2010, at 4:37 PM, Ray Sills wrote:
> The difference in power between 50 watts and 100 watts is essentially insignificant.

Whether 3 dB of power difference is important depends on band conditions.

Alex (Mr. CW Skimmer) VE3NEA has a nice set of measurements that he'd made a few years ago at

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

The AWGN (Additive White Gaussian Noise) condition is basically the case of a quiet band (single path with no Watterson spreading).  Notice that a 3 dB change in SNR can take you from practically perfect printing to no printing at all.  The blue curve is what you see in textbooks for binary FSK.  The others are three amateur software modems that he'd measured.

On the other hand, in the presence of selective fading or flutter, a 3 dB power change won't improve the character error rate by very much, you need 10 dB of power change to transition the RTTY decoding threshold.

73
Chen, W7AY