[TowerTalk] best coax/receiving

[Ian White, G3SEK]

WA4DOU wrote:

>a few tenths are not
>even discernable. This is, after all, a technical avocation, and it
>revolves around the laws of phisics. Our ability to measure gain is
>limited to about +- 1 db, under the best of conditions. And a db (1 db)
>is "just barely discernable."

That is incorrect on at least three counts.

1. The discernability of a few tenths of dB is by no means a "law of
physics". It's merely an attempt to generalize some experimental data.

2. The experiments were about the ability to discern a change at HIGH
signal/noise ratio, where the reference point is the subject's memory of
the level before the change. Discernability at low s/n is likely to be
very different, because a comparable level of noise is continuously
present as a reference.

3. You are only addressing signal/noise ratio. Contesters and weak-
signal operators measure the value of a dB by its effect on their
ability to COPY information from a weak signal, and ultimately on the
total SCORE in a long contest. Signal/noise ratio has an effect on both
of these, but not in a simple way.


73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.com/g3sek

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