# RF

Discussion in 'Wireless & RF Design' started by abdulsamad4321, Jun 23, 2014.

Nov 24, 2013
30
0
Please tell me relation between frequency and free space loss. Which frequency is better to trnasfer data 900MHz or 1800MHz?
Thank you.

2. ### BR-549 Well-Known Member

Sep 22, 2013
2,164
415
Ok. Co = speed of lite. Eo = electric permittivity. Uo = magnetic permeability. In free space......Co = 1/EoUo. Which frequency you use will depend on local and regional environment and topology.

3. ### dougc314 Member

Dec 20, 2013
38
11
read up on "free space path loss" on Wikipedia, there is an equation.

At first glance people think that for higher frequency there is more loss, and therefore higher frequencies can't work as well. If you are constrained by antenna gain, that is so. However antenna gain is based, generally, on the relative (in wavelengths) of an antenna's effective area, which is similiar to its actual area if the antenna is designed correctly. So, at higher frequencies a certain size antenna will have more gain then at lower frequencies, and that can make up the frequency "penalty" However if you need antennas with a certain directivity, say omnidirectional then yes, path loss increases with 1/F^2. (But the required antenna gets smaller)

To answer which band is better depends on many things other than just free space path loss.