George ,

Differences like that are generally expressed as ratio of powers
so 3 w compared to 5W is about -2DB less.  or 5W compared
to 3W is 2DB more.

Now the guy at the other end has his Hilberling and is observing you. 
first is  a full s unit is 6DB to get that increase at his end you would have
to double your power.  Why is that so, Smeter is detectd voltage and power 
is a different scale.  So to move 1 S unit (on a calibrated radio, most are not)
you hav eto double your power.   So going from 3 to 5 is not double.
If your signal was marginal it would maybe help.

Of course if you went to 25W that's,  10* log10 of (25/3 ) = 9.2db,
and he would certainly hear that and see it on his meter.  Its why people
say at round 4W you really should not bother for less than about 16W
or about 6DB power increase.  (hint: double twice is 6DB).

So on a power basis tweaking for less than 2:1 change is low value
save for its class E.   If it is dialed in its power consumed and heating
is lower as compared to not dialed in.  Different reason and only loose
coupling to his S meter.  Less power wasted, less heat, less battery drain.

Allison
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