This can be a "fool's errand" ... from the economic side (In finance, this is sometimes referred to as "diminishing returns").
Look at the diagram in the upper right of this web page:http://www.phys.unsw.edu.au/~jw/dB.html
Notice you are NOT dealing with linear relationships (this use to be a standard exam quesiton for an Amatuer Radio License) - AS your move to the right (MORE POWER) the resultant increases in dB level are not as significant.
IF you desired to increase your dB (and be heard well on the other side) - IMPROVE your antenna system!
A 100 feet of poorly installed coax can easily rob 1 to 3 dB before it even reaches the antenna. Another analogy: "I want more water pressure since my irregation systems has leaks, corroded sprayers, ut I don't want to do the work to fix these"
dB is an abbreviation for "decibel". One decibel is one tenth of a Bel, named for Alexander Graham Bell. The measurement quoted in dB describes the ratio (10 log power difference, 20 log voltage difference, etc.) between the quantity of two levels, the level being measured and a reference. To describe an absolute value, the reference point must be known. There are a number of different reference points defined. Here are a few:
+ dBV represents the level compared to 1 Volt RMS. 0dBV = 1V. There is no reference to impedance.
+ dBu represents the level compared to 0.775 Volts RMS with an unloaded, open circuit, source (u = unloaded).
+ dBm represents the power level compared to 1 mWatt. This is a level compared to 0.775 Volts RMS across a 600 Ohm load impedance. Note that this is a measurement of POWER, not a measurement of VOLTAGE.