From: Bob kb8tq <[email protected]> >>>> - high-Q crystals require SC-cut >>> ... An SC has a lower Q than an AT of similar size >>> and design up to the point acoustic Q losses completely take over. >>> If you are talking about sub 20 MHz OCXO?s with ?doable? crystal >>> package sizes, the AT will have the higher Q by a significant margin. >> >> Could you please back up this claim with verifiable facts? > > Order up a few 5 MHz 3rd overtones in HC-40 packages and see what you get. > You also could send in an RFQ for a batch of each to any of the people who > make them > and see what comes back. > Bob
Here is a random selection of links to back my point of view that, if you have noticed, contradicts Bob's. If anybody is interested they will find information themselves without much effort. I suggest printed books if you don't trust Internet at large. http://www.crovencrystals.com/croven_pdf/Old%20Spec%20Sheets/croven_catalogue.pdf (Croven Crystals is Wenzel company) The main advantages of these resonators, and in particular the SC-cut type are: higher Q-factor (typically 10 - 15% better than equivalent AT-cut resonators) https://www.tfc.co.uk/pdfs/SC_cut_crystals_article_TFC.pdf SC cut family of quartz crystals: Other key characteristics include Higher Q factor https://www.rfwireless-world.com/Terminology/AT-cut-vs-SC-cut-quartz-crystal.html Specification:Q factor AT cut: lower SC cut: higher (it will achieve low phase noise) http://members.femto-st.fr/sites/femto-st.fr.patrice-salzenstein/files/content/Peer-review-journal/smdo160017.pdf SC-cut It has faster higher Q, warm-up speed and better phase noise close to the carrier. http://www.resonal.com/Downloads/John%20R.%20Vig%20-%20tutorial%20on%20Quartz%20Crystals%20and%20Oscillators.pdf Advantages of the SC-cut: Higher Q for fundamental mode resonators of similar geometry http://www.mtronpti.com/sites/default/files/files/crystal-resonator-terminology.pdf A typical 10 MHz, 3rdovertone SC may have a Q of 1.0 to 1.3 million; a 100 MHz, 5th overtone AT may have a Q of 80 to 100 thousand, while a 100 MHz AT fundamental would be much lower, in the range of 20 to 50 thousand. https://www.eetimes.com/document.asp?doc_id=1290592# (MptronPTI) Since SC-cuts have a much higher Q-factor than AT-cuts, SC-based OCXOs offer better noise performance from 1-Hz offset to 1,000-Hz offset. Worryingly, I have started receiving unpleasant personal emails from list members suggesting that I do not question factual correctness of other's opinions. This will explain why I am going off the list for the sake of everyone's good. Leo Bodnar _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
