The circuit diagram for the PMC servo card is D980352. From this diagram, I see that I can send an excitation from the network analyzer to FP2TEST (9.09 kOhm input impedance) where it is added to the PMC error signal before going to the loop filters.

I hook up the following

• Agilent 4395A output to SR560 (300 Hz HP, gain of 1)
• SR560 to FP2TEST and to Agilent's channel R
• PMC error signal IF (mixer box mounted to rack, I noticed the IF BNC->SMA were a bit loose/stressed by a hanging LP RF filter) to SR560 (also 300 Hz HP, gain of 2)
• SR560 to Agilent channel A

I 'Enable' Test 2 on the PSL screen, so FP2TEST gets added to the error signal.

PDH signal

• TDS 3034B with four channels
  • 1. PMC servo box external drive (split off from the function generator)
  • 2. PMC servo box output monitor (mirrors the drive, shows when drive is saturating)
  • 3. IF signal (split off after the mixer)
  • 4. PMC Trans (long BNC from the PSL table)
• SRS DS345 function generator (into the PMC servo box' external drive)
  • 100 Hz signal (there's a 10 Hz pole on the PZT drive, so any faster than this and I can't see both sidebands without the HV output mon clipping)
  • 3.19 Vpp amplitude (smallest amplitude at 100 Hz such that both sidebands are well resolved)
  • 1.52 V offset (center the carrier's PDH error signal at pi/2 out of phase with the drive)

I was able to see the carrier and both sidebands.

I tried to grab this data from the scope via ethernet, but was unsuccessful (timeout errors, I'm using the scripts from scripts/tektronix/tek-dump, and the GPIB box that Kruthi had been using for the GigE cam; I also tried plugging in directly scope->ethernet. Never got anything but timeout errors, so maybe I'm not specifying the port correctly. Anyway the trace is frozen on the scope for later use, or I can easily repeat this now that I know how).

Spectrum

Next, I locked the PMC (Test1 is off, tune DC output adjust until I get some transmission, turn on the loop at Test1, increase the gain to before the loop goes unstable). I'm sending the following channels to SR560 (gain = 2, no filtering, high dynamic reserve, 50 Ohm outputs), and reading spectra from the Agilent 4395A:

• R-- PMC TRANS PD
• A-- PDH IF
• B-- PMC PZT HV MON

The HV mon was always saturating the preamp, so I disconnected it; I added a 50 Hz (6db) high pass to the Trans PD signal, since it has a DC component.

I got to take a look at the traces on the spectrum analyzer front panel, but too tired to do the GPIB for now. There are peaks, things look reasonable.