three cables connecting the amplification module to the analog-to-digital conversion module. To reduce this current to less than 0.005% of the differential mode current, additional clamp-on ferrite cores are placed every meter on the transmission cables.

Finally, the analog-to-digital conversion is accomplished with an Acqiris AC240[^3] 8-bit digitizer with maximum dynamic range of 48 dB (although, in practice, the effective dynamic range was substantially lower due to coupling between the digital output of the converter and its input). The AC240 uses an embedded field programmable gate array (FPGA) to perform onboard Fast Fourier Transform (FFT) and integration of the power spectrum in realtime. The spectrometer is clocked at 1 GS/s and the Fourier transform processes 16,384 channels, giving a bandwidth of 500 MHz and a raw spectral resolution of about 30 kHz. The broadband spectrometer employs the FPGA code of and a Blackman-Harris window function is used to improve the isolation between neighboring frequency channels at the expense of reducing the effective spectral resolution to 122 kHz. The unit is contained on a CompactPCI card connected to a host computer. The digitizer and host computer, along with a power transformer and interface circuitry for controlling the amplifier module with the 