I understand the formula for calculating the far field distance from an antenna is:
Distance = (2D2)/λ
Is the D in the above equation the length of the antenna under test (antenna under test is a small PCB antenna)? In which direction (1 or 2 in the image below)?
Whilst trying to research this, I came across an image [Source]
But I was sure the formula for converting between wavelength and frequency was:
Frequency = 1/λ
Are there two formulas?