[TowerTalk] dx blaster antenna

[Gary Schafer]

No such thing as a "voltage" db verses a "power" db. It is all the same.
The db is an expression of the ratio of one power level to another power
level.

2 times the power is a 3 db increase in power.
Or 10 times the power is a 10 db increase in power.

2 times the voltage will be a 6 db increase in power.
Or 10 times the voltage will be a 20 db increase in power

Your S meter is a power meter.

Here is an example of how voltage and power are related.
For 100 watts it takes 70.7 volts across 50 ohms.  P= E squared /R. good old
ohms law at work. 70.7 x 70.7 = 4998.49 or 5000 rounded. Divide 5000/50 ohms
= 100 watts.

If we double the voltage (70.7) to 141.4 and find what power that represents
we have 141.4 x 141.4 = 19993.96 or 20000 rounded. Divide 20000/50 ohms =
400 watts.

Notice that when the voltage doubled the power increased by 4 times. 4 times
the power is equal to 6 db increase in power level. 

73
Gary  K4FMX


> 
> Isn't the S-meter measuring voltage dB's  (20xlog)
> 
> Is that why I normally see a 20dB (voltage) S-meter increase when a
> station increases power from 100 watts to 1000 watts.
> 
> 
> Mark N1UK