[SOLVED] Anechoic chamber in Faradays Cage.

Hello,

I am taking some measurements in the anechoic chamber which is placed inside a Faraday's Cage, using a radiometer. The signals that we are dealing with a very low power signals i.e. something from a heat source. There are two different things happening:

P.S. (These measurements are compared with the Hot and Cold references )
1) When the heat source is placed outside the anechoic chamber and allowed to cool down a good variation is observed, depicting the cooling of the tile. But the tile appears to be much hotter than expected and the trend lies outside the references used making us feel that the antenna is picking more signals than expected.

2) When the heat source is placed inside the anechoic chamber and allowed to cool down, no variation is observed. These measurements lie within the references.

All I want is that the variation to be observed within the reference levels and not any hotter.

Any Suggestions or reference material is welcome.

Thanks in advance.

Sounds like an electromagnetic interference issue. But you didn't say a word about the involved instruments, e.g.
the "radiometer" type. It's not clear, if a response to enviromental RF can be expected as normal operation.

The radiometer that we are using is a "total power radiometer" and it is used along with a RF switch, switching between the hot, cold and the target scene cyclicly. This means that the calibration points are collected along with the scene almost simultaneously.
The return loss of the antenna used for measurement is greater than -20dB at the required frequency.

making us feel that the antenna is picking more signals than expected

Click to expand...

You didn't tell any reason, why you don't expect to receive RF from various enviromental sources.

You didn't tell any reason, why you don't expect to receive RF from various environmental sources

Click to expand...

I am trying to collect signals from a heat source isolated from the environment. That is the reason for enclosing the heat source in the anechoic chamber, so that any other external interference is eliminated.

The antenna having a return loss of <-20dB is used but I wonder if very low power from the heat source and moreover that fact that a considerable amount is being absorbed by the absorbers is making the signal attenuate.

In your original post, you reported expected results for measurement in the chamber but deviations (receiving more energy)
outside. In my opinion, this behaviour can be simply explained by RF/microwave interferences.