At 10:58 AM 2/11/05, Paul Kelley wrote:
>Being a weak signal CW operator I can tell you that ONE dB
>(or less) can make the difference between a contact and no
>contact.... if you don't think so, you have not spent
>several years working EME!
I think this thread is the first time I've ever heard a debate over whether
3db is audible. I've always heard that ONE db is a barely audible
difference, and as Paul notes, EME operators strive for tenths of a db
improvement.
>But getting back to FM and repeaters... I have seen a lot
>of this 3 dB is / is not significant debate over the years.
>Maybe it depends on what you are trying to do. I would
>agree 3 dB is not noticeable or barely noticeable if the
>signal is already well out of the noise. However, in areas
>where you are trying to push repeater coverage from a given
>site to the limits, 3 dB is significant on the outer
>fringes and in the problem areas. I say this from personal
>experience. I have seen 3 dB change in repeater power or
>antenna gain make a significant and consistent improvement
>in fringe/weak areas. It can be enough to make the
>difference between the repeater being usable or not... I
>call that significant.
Again I agree with Paul. The quieting curve of an FM receiver is very
non-linear. 3 db will make a very noticeable difference if the signal is
well into the noise, barely any or none at all if it's strong. The result
is that a 3 db improvement will in most cases approximately double your range.
Roger Grady K9OPO
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