Not logged in
Wed Jul 2 00:59:13 2008
balanced detection, noise plots, progress
Progress report submitted today(!). It is on the 40m wiki page. Below is a figure of some estimated noise sources.
Made voltage divider that acts as an attenuator for one of the paths in the Mach Zehnder, which should help to balance the detection and reduce noise.
First tested using a 636 Hz Matlab generated audio signal (thanks to John inspiration on portable headphones). Figure is attached, with plots of noise spectra of original and optimized signal with and without added acoustic noise (visible as peaks as 636 and 1272 Hz, linewidth approx 4 Hz). My first try at optimization reduces the noise by nearly an order of magnitude for most frequencies.
Will work on finding different noise source to better see what happens at low frequency, and try to get finer control of tunable gain.
Uploaded Wed Jul 2 02:04:32 2008