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Entry  Wed Sep 26 16:59:17 2018, anchal, Summary, FSS, Characteristics of new RFPDs in FSS NorthandSouth_35500kHz_RFPD_Measurements.pdf
    Reply  Mon Oct 1 23:44:59 2018, rana, Summary, FSS, Characteristics of new RFPDs in FSS 
Message ID: 2240     Entry time: Wed Sep 26 16:59:17 2018     Reply to this: 2244
Author: anchal 
Type: Summary 
Category: FSS 
Subject: Characteristics of new RFPDs in FSS 

We installed new RFPDs with components s.t. they are tuned near 35.5 MHz. We tuned the inductor L1 and capacitor C40 to bring the peaks and notches to desired values. Attached are TFs and dark noise measurements of these two photodiodes. The transfer function measurements are adjusted with the transfer function of the cables up to the photodiodes. The photodiodes were blocked with a beam dump during measurements and are supplied with +-18 V through the new power strip under the table. In the analysis, 2000 Ohms of DC transimpedance is assumed for TFs. Note: This was a wrong assumption. So do not trust the y-axis. This is a transfer function measurement through test-in ports which could be wrong.
Following are some measured numbers:

South Path:
SN 010
RFPD tuned to 37 MHz.
Notes:
Inductor L1 changed to 146-06J08SL
+5V regulator LM309H replaced with new one.
Measured Peak at 36.882 MHz
Measured Notch at 74.237 MHz

North Path:
SN 009
RFPD tuned to 36 MHz.
Measured Peak at 36.247 MHz
Measured Notch at 72.356 MHz

Conclusions:
Except for South RFPD being low Q (as it was written on it). the two RFPDs have similar response and same amount of dark noise. This should reduce the contributions from south path in the excess noise measured in the last BN measurement.

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