Hi Robert in the days before TTL dividers there were quite a few vert low frequency cuts. I think that one is a flexural bar designated "NT cut". I have also seen crystals of lower than that made in the "gapped ring" format which oscillate a little like a tuning fork. ( I think I have seen one of these cut for 440Hz, but a 1Khz gapped ring would fit in an Int. Octal GT envelope.)
I think on your sample the supports are about 25% of the distance from the ends. these are the nodes of the mechanical vibration. You may well be right about the extra excitation electrode. These big chunks of quartz are quite difficult to get moving I believe. Their stability is nothing special but is a lot better than any other form of electronic resonator at the time. It probably dates from the early 1950s. Alan G3NYK ----- Original Message ----- From: "Robert Atkinson" <[EMAIL PROTECTED]> To: <time-nuts@febo.com> Sent: Tuesday, May 20, 2008 1:32 PM Subject: [time-nuts] Low frequency crystal > > > Hi, > > I just found a 1000c/s (yes 1kHz) quartz crystal at a local radio car > boot sale. It's a NOS GEC "Quartz Crystal Unit" type DJC/669. It's in > an overlength minature valve (tube) glass envelope. The crystal is a > long slab with 3 connections. The 3rd connection seems to be a small > (feedback?) electrode. > > What's the lowest frequency crystal made? Anyone have any suggestions > for an oscillator circuit? > > Robert G8RPI. > __________________________________________________________________ > > Sent from [1]Yahoo! Mail. > A Smarter Email. > > References > > 1. http://us.rd.yahoo.com/mailuk/taglines/isp/control/*http://us.rd.yahoo.com/e vt=52418/*http://uk.docs.yahoo.com/nowyoucan.html > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.