A Dielectric constant of air with temperature change

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1. May 6, 2018

Antenna_Ed

I'm looking to see how much the dielectric constant of air will change mostly as a function or air temperature.

Is there a formula that outputs air dielectric as a function of temperature or atmospheric pressure?

2. May 6, 2018

Ffrenchy

If using a capacitor you might be able to use C=Ae/d but I really donâ€™t understand your question fully

3. May 6, 2018

Antenna_Ed

Let's pretend I have a source antenna outputting a 1 GHz. I have two receive antennas on the main lobe. One is 10 meters away and the other is 11 meters away. I do my measurement at 25 C. I'm going to get some phase delta between these two antennas.

Now if the temp is 15 C when I make the measurement, what will the phase delta be? I'm ignoring everything else at the moment and only care about the effect of air. If I knew the dielectric I can compute the velocity factor and know the magnitude of change.

4. May 8, 2018

Funestis

Intuitively, I would expect permittivity to increase with an increase in temperature. The relative permittivity is directly related to electric susceptibility, and I believe there are a number of publications that exist discussing the subject of the dependence on electric susceptibility of air with temperature. I haven't done a lot of research on the subject, but I would start there.