Kiwamu, Aaron, Rich. A

Installed and tested RF cabling for LSC and ASC detectors on ISCT1 (LSC-POP-AIR-A, LSC-REFL-AIR-A, ASC-REFL-AIR-A, ASC-REFL-AIR B).   All cables are ~41 feet long LMR-195 type cable from the ISC racks to the outer wall of ISCT1. 

The RF loss from the RF patch panels in ISC-R2, to the outer wall of ISCT1 is 0.6 dB at 9MHz, and 1.2dB at 45MHz.  All cables tested are +/-0.1dB of these numbers.

In preparation for installation of the in-air and in-vacuum RFPDs on ISCT1 and HAM1, we tested every signal chain (ASC and LSC, air and vacuum) by injecting a 0dBm RF signal offset 0.5 Hz from each respective modulation frequency and viewing the beat note in Data Viewer and on a scope locally at the front panel monitors of the I/Q demodulator chassis.  The goal of this was not to accurately calibrate each signal chain (this happens once the respective detectors are in place), but to verify proper plumbing and get a sense of the overall consistency in signal detection.  The results are remarkably good, in that all RF gains from demodulator inputs to Data Viewer output were within our measurement certainty of ~+/-5% or so.

Here's a sense for what you can expect for an RF injection directly at the input of the I/Q demodulator at 0.5 Hz offset from the modulation frequency:

Input RF Test Signal Amplitude = 0dBm +0dB, -0.5dB
Beat Note Frequency = ~0.5 Hz
I/Q Demodulator Front Panel Monitor Amplitude = ~3.45 V pk-pk
Data Viewer Amplitude = +/- 5500 counts pk-pk

The data taken on the LSC-REFL-AIR-B-135MHz signal showed more like +/-5000 counts pk-pk, and a Front Panel I/Q Demodulator Monitor amplitude of 3.5 V pk-pk, but because we didn't have a function generator that went up that high in frequency on hand, we used the RF network analyzer as the signal input.  The signal amplitude uncertainty could easily account for some of the difference in demodulating the 135 MHz signal.

Tomorrow we are expecting a 9 and 45 MHz LSC style detector to be delivered.  This will be placed on ISCT1 as the LSC-REFL-AIR-A detector and the light to counts transfer function will be measured.  The plan is to create a simple written guide to this type of measurement such that calibration and recalibration is easy for anyone to do.  We will use the dedicated ISC RFPD calibration light source to inject a signal.