Hi Early in the WWII era, quartz blanks were not commonly etched after begin ground / polished to frequency. This left debris on the surface of the blank. The net result was that the resonators failed after a period of time in the field, especially under damp conditions. The problem got so bad that it actually threatened the ability to communicate in 1942. A fairly high level team looked into the issue and etching of blanks (and a few other mods) were made a mandatory part of all crystals suppled to the government. Ammonium bi-flouride and water was the most common etchant in that era. There are a number of papers about the whole deal in the FCS, and many stories told by those who were part of the changes.
Bob On Apr 21, 2014, at 10:10 AM, J. Forster <[email protected]> wrote: > No. There is just a little rectangular quartz wafer. No plating. > > In fact, post WWII, when many ham transmitters were 'rock bound' (ie: > crystal conteolled) it was common pratice to regrind mil surplus rystals > to move them into the ham banda. > > Apparently, some were also etched using a cleanser called Whink, which > contains a flourine compound. > > Also, some advocated applying graphite from a pencil lead was used to > decrease the frequency. > > If the crystal ativity was low, they were taken appart and cleaned. > > > > -John > > ============== > > > > >> I'm puzzling over this statement. The FT-243's I have seen have a spring >> that squishes the quartz blank between the electrodes. They aren't plated >> onto the quartz, but they are still in intimate mechanical and electrical >> contact. >> >> -Chuck Harris >> >> Bob Camp wrote: >>> Hi >>> >>> The WWII era FT-243 is one example of a crystal that has the active >>> portion of the >>> electrodes separated from the resonator by an air gap. There are lots of >>> similar >>> holders from that era that do pretty much the same thing. Non-contacting >>> electrodes are not very new. >>> >>> Bob >> _______________________________________________ >> 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. _______________________________________________ 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.
