Pls help on power gain

[Bignyut]

Question;
Given that a dipole antenna has directional gain of 2, calculate the power gain in Dbi?

Answer;
Power gain = 10 log (x/y), where y =1
Power gain = 10 log (2/1) = 3dbi

My question is….how come y = 1??

Thanks in advance

 

[wwfeldman]

10 log(x/y) = 10 ( log(x) - log( y ) )
y = 1 is gain of 1
x = 2 is gain of 2
need to reference gain to something when express it in dB
gain of 1 as a reference is perfect

 

[Bignyut]

10 log(x/y) = 10 ( log(x) - log( y ) )
y = 1 is gain of 1
x = 2 is gain of 2
need to reference gain to something when express it in dB
gain of 1 as a reference is perfect

Thanks.
Am I right to say y=1 is standard?

So if another question become directional gain of 3,

My answer will be
10 log (x/y) = 10 log (3/1)?

 

[wwfeldman]

yes