[time-nuts] need help with LPF

SAIDJACK at aol.com SAIDJACK at aol.com
Mon Apr 12 19:42:39 EDT 2010


 
Hello guys,
 
need some help please:
 
I am looking for suggestions on a problem I have with a 20MHz LPF.  This 
part is used to reduce harmonics when generating an nice 10MHz  sine-wave. Any 
help is appreciated.
 
We are using a ceramic 560nH 0603 inductor, and believe that this part  is 
picking up lot's of noise around 500Hz to 1KHz when on the vibration table.  
Makes the Phase Noise of the Oscillator more than 20dB higher than without  
it!
 
The caps used in the filter are small COG types, so I don't think they are  
the ones causing the microphonic sensitivity.
 
I am thinking that a wire-wound inductor fully encased in epoxy would work  
better.
 
We could also use off-the-shelf filters, such as the Mini Circuits  
SLP-21.4+ SMA-to-SMA type filters, does anyone have any experience how  these will 
perform under vibration?
 
Any hints anyone?
 
Thanks much in advance,
Said



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