I've got an EMC testing setup of a 1 meter shielded tent, and a very high gain EMC antenna.
I'm seeing a phenomena that I can't quite explain.
I have a known product that was tested in an accredited 3 meter chamber.
I have a known comb generator that was also tested in a 3 meter chamber.
(dbuV/m are approximate):
In the 3 meter chamber, the comb generator at 100MHz is 40 dbuV/m (that's right at the Part 15 limit).
In the 3 meter chamber, the known emitter at 100MHz is 43 dbuV/m (so it failed by a few dbuV/m)
So now I take the known comb generator, and put it in my 1 meter shielded tent.
In the 1 meter shielded tent, the comb generator at 100MHz is 50 dbuV/m (there are unknown cable losses, scenario not calibrated, etc... but bear with me).
Now I take the known emitter, put it in the 1 meter shielded tent, and at 100MHz the signal is 20 dbuV/m.
From the calibrated chamber readings, we know these should be the same value or very close to each other.
What sort of phenomena could I possibly be seeing? Could the comb generator, as an intentional transmitter, be reflecting in my tent and somehow increasing the perceived signal strength?