I took some steps to reduce the coupling of 60 Hz harmonics in noise measurement. The box was transferred to the floor instead of on top of another instrument. Measurement was immediately converted into single-ended using SR560 in battery mode with a gain of 10. All of the setups was covered in aluminum foil to increase isolation.

Spectrum measurement details

• Boards were powered by sorenson power supplies with +/- 18V DC.
• 36 Ohm load was connected to coil output port.
• Signal was taken out using clips from V2+, V2- and GND.
• Signal was first sent to SR560 in A-B mode with a gain of 10 in battery mode.
• The board along with SR560s were covered in aluminum foil to reduce 60Hz harmonics.
• The output from 50Ohm port was sent to SR785 and read with floating ground.
• Instrument noise was measured by shorting the clips with each other.
• Transfer function of measurement setup was measured and divided by final output.
• Measurements were taken with file D1100687_SP.yml and D1100687_SP_LF.yml.
• D1100117_S2100027_Voltage_Noise_Spectrum.pdf and D1100117_S2100028_Voltage_Noise_Spectrum.pdf shows the measured voltage noise spectrum at the output monitors when loaded with 36 Ohms.
• D1100117_S2100027_Current_Noise_Spectrum.pdf and D1100117_S2100028_Current_Noise_Spectrum.pdf shows the esitmate current noise through the coil calculated by dividing the measured voltage noise by 2436 Ohms.