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Message ID: 1997     Entry time: Tue Dec 5 21:50:05 2017
Author: Craig, awade 
Type: DailyProgress 
Category: PLL 
Subject: Low Noise RF Amplifier Added to  

We noticed the dang SR560 is injecting noise into our beatnote spectrum at high gain.  I found a ZHL-3A low-noise RF amplifier and we've added it in after the transmission beatnote RFPD and in front of the new mixer (ZX05-1MHW-S+) in our PLL loop to amplify our beatnote with low noise. 

Our beatnote is ~100MHz.  Amplitude is 2 dBm.  The noise figure of the RF amp at 100 MHz is ~5.5.  RF amplifies the beatnote to 19 dBm (we attached a 10 dBm attenuator to avoid saturation of our mixer, which is rated to 23 dBm RF input).


Before adding in the RF amp, the PLL OLG UGF is ~25kHz.  The SR560 gain is 20.  The Marconi FM Devn is 10 kHz/V.

After adding the RF amp, I took the same spectra with the same PLL settings as before to get a direct comparison.

The plot shows the direct comparison.  The pictures show the settings of the PLL.

 

Edit (awade) Thu Dec 7 21:23:50 2017: Put the actual part/model numbers.  Links die after a time, you need to actually list the part otherwise it will be a mystery.

 

Attachment 1: StitchedSpectrum_AfterRFAmp_PLLControlSignal_MarconiFMDevn_10kHz_SR560Gain_20_Avgs_30_Span_102p4kHz_05-12-2017_225050_Spectra.pdf  168 kB  Uploaded Tue Dec 5 23:33:26 2017  | Hide | Hide all
StitchedSpectrum_AfterRFAmp_PLLControlSignal_MarconiFMDevn_10kHz_SR560Gain_20_Avgs_30_Span_102p4kHz_05-12-2017_225050_Spectra.pdf
Attachment 2: StitchedSpectrum_AfterRFAmp_PLLControlSignal_MarconiFMDevn_10kHz_SR560Gain_20_Avgs_30_Span_102p4kHz_05-12-2017_225050.tgz  79 kB  Uploaded Tue Dec 5 23:33:36 2017
Attachment 3: 20171205PLLHardware.jpg  1.929 MB  Uploaded Tue Dec 5 23:33:52 2017  | Hide | Hide all
20171205PLLHardware.jpg
Attachment 4: 20171205PLLSR560Preamp.jpg  1.747 MB  Uploaded Tue Dec 5 23:34:02 2017  | Hide | Hide all
20171205PLLSR560Preamp.jpg
Attachment 5: 20171205PLLMarconi.jpg  1.842 MB  Uploaded Tue Dec 5 23:34:10 2017  | Hide | Hide all
20171205PLLMarconi.jpg
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