One of the first things we did was to put two dipole antennas into the chamber and scan for resonances.  Since neither antenna was calibrated and both were far from resonance the actual amplitudes of the signal do not have any particular meaning.  The data was taken on an spectrum analyzer with a tracking generator (-10dBm output) with a 100 kHz bandwidth.

Although the lowest theoretical resonance is about 248 MHz we seem to turn on at about 347 MHz with a Q of about 160.  We expect that the shift in frequency is due two brackets forming  loops on both sides of the chamber.  The low Q is probably due to the anodized steel inside the chamber (the material of the loops).