Koji met with awade and I today, and told us to understand our PLL noisebudget before doing anything else.  That way, we can know exactly what limits us and can be exact when we reduce noise.  Now the real work begins.

To make a proper PLL noisebudget, we are going to measure shot noise, dark noise, VCO noise, SR560 noise, PLL OLG, and calibrate everything into Hz/rtHz.  This will take a couple of days.

Today, I calibrated our mixer into mV/deg.  I figured out how to set up the Marconi master-slave using the 10 MHz frequency reference they have on the back, then set both Marconi's to 100 MHz RF out at +13 dBm.  I checked the 100 MHz output of each Marconi on the oscope (figure 2).  By adjusting the slave Marconi carrier frequency phase in the menus, I was able to control the relative phase of the PLL.

I then mixed the Marconis together.  I changed the phase from 0 degrees to 180 degrees, recorded the mixer output voltage, and plotted it in Figure 3.

I got a mixer calibration of 7.111 mV/deg at the maximum slope, or 407.4 mV/rad.

Next, we will use this to find the audio frequency noise of the Marconi by feeding the mixer output back to the slave Marconi.  More to come.