He had no way to quantify the "crud". There are many sources of it along the way.
His comments to me were aimed at the amount of contamination that takes place during the plating of the electrodes on the quartz blank itself as well as any "crud" that is left from the lapping of the blank. His main point was that it make take trial and error testing of say a dozen crystals to find the best of the lot for use in his ULN oscillators. My take is that 5MHz is not a fixed & magic number. Just a frequency that works well for today's frequency standards and can be divided or multiplied as needed. As another post on this thread said, there are a number of factors involved and while 1MHz might be "better", the size of the crystal becomes a trade-off. What I don't know fills MANY text books! -Brian, WA1ZMS -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Hal Murray Sent: Sunday, August 04, 2013 9:54 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 5MHz x 10MHz [email protected] said: > In a talking to Charles Wenzel about this very topic some 13 yrs ago, > I liked it when he said sometimes it comes down to the "quartz-to-crud ratio" > of the crystal that makes all the difference for a given crystal frequency. Neat. Thanks. How much crud is in a typical modern crystal? How much was in natural quartz, say from WW II era? I assume modern crystals are made from quartz grown in a lab using techniques similar to what the semiconductor industry uses. Are we talking ppm or ppb? Does anybody have any long term stability data on old crystals vs modern crystals? Yes, that's not very specific. By old, I'm remembering the crystals I saw as a kid (late 1950s). It was just a few screws to open the package. I expect the ARRL handbook had recipes for adjusting the frequency but my copy from those days is long gone. -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
