Topband: Demo of the value of one dB and the cost of sending too fast

[Bob Lawson]

I spent part of my engineering career designing satellite command FSK 
demodulators - including the deep space Pioneer Venus orbiter. To test 
the performance of them, we would mix the test signal with white noise.  
When you look at the FSK Bit-Error-Rate (BER) curve (bit errors versus 
signal to noise ratio in a bandwidth equal to the bit rate), you can see 
the BER improves by a factor of 10 to 1 for every dB in S/N ratio.  In 
other words, for every dB improvement, you get one tenth the errors.

73 de Bob N6RW

On 2/25/2016 9:40 AM, donovanf at starpower.net wrote:
> The weak signal CW recordings on AB7E's website are well worth
> a few minutes to listen to. His recordings clearly demonstrate
> -- much more convincingly than any other demo I've ever heard--
> the significance of one dB of improved signal strength and the cost
> of sending too fast under weak signal conditions
>
>
> http://www.ab7e.com/weak_signal/mdd.html
>
>
>
>
> My takeaways from his recordings:
>
>
> - its well worth the effort to improve your signal by as little
> as one dB
>
>
> - when signals are very weak, sending faster (especially
> at speeds faster then than 30 WPM) costs the equivalent of
> many dB of reduced signal strength.
>
>
> If you haven't already clicked on AB7E's webpage, these are
> direct links to several of his recordings.
>
>
> A weak CW signal buried in noise with the signal strength
> decremented in one dB steps,
>
>
> http://www.ab7e.com/weak_signal/6_5_4_3_2_1_0_db.mp3
>
>
>
>
> Two weak CW signals buried in noise -- slightly offset in
> frequency -- with one signal one dB stronger than the other:
>
>
> http://www.ab7e.com/weak_signal/A_vs_B_1db_v1.mp3
> http://www.ab7e.com/weak_signal/A_vs_B_1db_v2.mp3
>
>
>
>
>
> Two weak CW signals buried in noise -- slightly offset in
> frequency -- with one signal two dB stronger than the other:
>
>
> http://www.ab7e.com/weak_signal/A_vs_B_2db_v1.mp3
> http://www.ab7e.com/weak_signal/A_vs_B_2db_v2.mp3
>
>
>
>
> CW signals sent at 20, 25, 30 and 35 WPM when buried in noise.
>
> http://www.ab7e.com/weak_signal/A_vs_B_2db_v2.mp3
>
>
>
> 73
> Frank
> W3LPL
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>