10 MHz hyperstable quartz oscillators performances

New hyperstable quartz oscillators are presented. Methods to overcome limitations due to various noise sources are discussed. Stabilities down to 5.10/sup -14/ are obtained together with drift down to 5.10/sup -12//day and excellent resistance to bad environmental conditions. Progresses in minimizing oscillators phase noise have, in fact, been very slow. Short term stabilities lower than 10/sup -12/ began to be obtained 30 years ago. The first result lower than 10/sup -13/ was obtained in 1978 but could not be reproduced until the 90's. More recently, quartz oscillators with exceptionnally good short term stabilities were needed for various projects including cold atom space clocks in France and Linear Ion Trap Standard in United States. More precisely 10 MHz quartz oscillators with stabilities in the vicinity of 7/spl times/10/sup -14/ between 1 and 100 s were studied and designed. In view of this work, it has been necessary to study all different possible sources of noise so as to undertake noise reduction when possible for instance in resonator and in the electronic circuits. Various attempts to reduce noise in the oscillating loop are presented. The most recent results obtained in France and in United States on several units are presented and discussed pointing out that it seems now possible to routinely build such units.