Saturday, May 7, 2011

Crystal Test Jig

Crystal Test Jig

Made up a test jig for testing the crystal.  It uses a 1k and 220 ohm resistor at each end and then two caps 10pf and 28pf so you can measure the fs1, fs2, fs3 and fp frequencies of the crystal and put them in the calculator at 

This will give the motional parameters of 
Cs  = crystal series capacitance
Ls =   crystal series inductance
Cp =  crystal parallel capacitance 

This values can then be used to empirically design a filter using the AADE filter design program at 

Using the simple Sig Gen I am not yet confident of the values enough to build a filter but after three attempts I think that I am seeing enough correlation to begin to at least play with the values in the filter design program.

I have reread the basic few paragraphs in SSDRA (Solid State design for the radio amateur) and EMRFD (Experimental Methods in RF design) and am continuing to learn.  

It will be possible to make a good filter out of the crystals that I have obtained but it may not be close enough to the stock Center Freq of the original Drake filter to work with the other filter.  Using a single carrier oscillator between the two filters to give both LSB and USB the filters need to have center frequencies about 3kHz apart.

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