Measuring radiation efficiency of antenna with different dielectric constant

Hi every one.

I want to make an experiment about impact of dielectric constant on embedded antenna.

I design a loop, put it into an insulator block, surrounded by a lossy liquid. Fix size of this lossy liquid

When I change dielectric constant of insulator, I need to change size of antenna to have the same resonant frequency.

Is this meaningful if I compare radiation efficiency of antenna with different sizes? And can I conclude that Some dielectric constant can give a high radiation efficiency?

Many thanks

Should be fine to compare antennas with slightly different sizes if they resonate on the same frequency (size changed due to different Er).
Usually, lower the dielectric constant between ground and the radiating element, higher the antenna gain.

Thank you for your answer.

But I want to change dielectric constant of insulator from 1 to 50, so Size of my loop antenna changes dramatically.

I just want to evaluate impact of dielectric constant on my loop antenna, inside a lossy liquid.

Is there any reliable way to do that? Because I think that when size of antenna is different, efficiency comparison is unfair.

Many thanks

If the antenna aperture (size) is totally different you cannot compare two antennas in terms of efficiency.
I think better is to not compare the antennas, and just check if the efficiency of the antenna inside of the liquid meets your requirements.
Anyway, an antenna inside of a liquid will never work like an antenna in free air.