There is no use making a FM antenna if there is no enough Signals coming from transmition stations, (due to obstacles,Weather, etc.....it can reduce the power of the wave form.)
I don’t know in which country you are...FM broadcasting Stations are not in a one particular place in most countries.(Not only FM, UHF & VHF as well). One station is in north & the other is in south………. So you need to rotate the antenna to focus each stations. This will not be a problem if you have All the broadcasting stations in a one place, so you need to Focus only to a one direction.
Simple steps to calculate the length of the dipole.
Note:the number after the decimal point represent superscript
Code:
V = velocity of the waveform (3x10.8ms-1)
F = frequency (Hz)
λ = length of one cycle of the 360.D waveform (m)
FM range 88 MHz to 108 MHz
Avg F = (108+88)/2 MHz
= 98 MHz
Applying V = F λ formula
(3 x 10.8) ms-1 = (98 x10.6) Hz x λ
300/98m = λ
3.0612m = λ
In λ/2 maximum voltage will present in the middle of the λ/2 conductor.
So the length of the dipole will be λ/2 = 1.5306m
If you need only for 102.6 MHz replace F in the formula & calculate The value of the dipole.