QH 40 A - High Stability Crystal Oven

Reference - QH 40 Hight Stability Crystal Oven

High Stability Crystal Oven based on the Principle of Zero Temperature Gradient

By Rex Moncur, VK7MO

Karlquistetall of Hewlett Packard, discussed the theory of Zero Temperature Gradientcrystal ovens that can produce improvements in frequency stability withtemperature by a factor of 20 or more compared to conventional ovenoscillators. The techniques used by Karlquist lead one to think aboutwhat might be possible with amateur home brew construction. This has ledto the concept of a modified Zero Temperature Gradient oven based on aconventional oven in conjunction with six low-cost DB6NT precisioncrystal heaters that actively maintain a zero temperature gradientwithin a diecast box. The modified Zero Temperature Gradient Oven has astability* of better than 1 Hz at 1296 MHz, or one part in 10^9th.

* Stability measured in the home environment over 24 hours with ambient temperature variations of 5 degrees.