[Premium-Rx] Measurements on Racal 9400 OCXO

[Stein-Olav Lund]

Hello,

I did some measurements on the "jumpy" reference oscillator in my
frequency counter mentioned some days ago.

I connected an ammeter into the +12V feed to it and measured the freq
from cold with a warmed-up

Fluke 1900A.

 

 

Time from switch-on (min)          I supply (mA)    Output freq (kHz)

 

0                                             350
5000.200

3                                             150
5000.008

6                                             120
5000.008

12                                            90
5000.060

20                                            90
5000.055

 

After this time the freq hovers around this value (around +12 ppm)

>From 3-6 min after switch-on it is OK, about 1.6 ppm off. 

The oven has a trimmer, careful adjustment (a half turn to and fro
factory setting)

doesn't seem to affect the frequency.

The supply current starts high, oscillates each 5-10 secs and settles.

Does this indicate to a bad quartz crystal?

 

Vy 73 de Stein LA9QV