RF power meter circuit
What would the best approach be to effectively measure the RF power?


Strictly speaking if you are to measure the RF power then you should be beyond the fresnel zone and in the far field: -



Only in the far field can you measure power. In the fresnel zone and closer an RF power EM wave hasn't properly formed but you can measure E and H fields as individual items.

A generally accepted rule for dipole type antennas is that the far field starts at approximately one wavelength distant from the antenna. For 433 MHz this is about 0.7 metres. This kind of makes your experimental measurement device quite big (in order to measure the more reliable far field RF waves). Also don't forget that reflections from walls and moving objects around your experiment can cause significant misleading results and you may find that shielding plays a big part in getting this to work.

Going for a more "focused" antenna won't help either because the fresnel field extends with antenna directivity.

The trouble with measuring the near-field fields is that they are complex in pattern and may not alter linearly with movement. They are reactive and and positioning a receive antenna in the vicinity can cause strange effects due to interactions.

This is why a lot of measurements of this type use microwaves (maybe 10 GHz).

However, don't be put-off by what I'm saying, just be prepared for odd results and hopefully, these words will give a little help in preparing you for the strange things you might encounter.