[time-nuts] Problems with a FRK-L

[Ulrich Bangert]

Sorry, forgot to set the topic in the first mail

> -----Ursprüngliche Nachricht-----
> Von: Ulrich Bangert [mailto:df6jb at ulrich-bangert.de] 
> Gesendet: Dienstag, 13. September 2005 16:29
> An: Time nuts (time-nuts at febo.com)
> Betreff: 
> 
> 
> Hi Folks,
> 
> i own a Efratom FRK-L which started into making trouble since 
> the last time i switched it on. I monitor the "lamp voltage" 
> as well as the VCXO control voltage. The unit locks a few 
> minutes after power up. But then the VCXO voltage is kind of 
> "noisy" and unstable. While it formerly came to a very stable 
> value with changes only in the microvolt region after some 
> hours of warming up, now the VCXO control voltage jumps 
> around in a 50 mV peak to peak region and sometimes it would 
> even loose lock at all. 
> 
> The "lamp voltage" is close to 7.00 V and very stable, so i 
> do not expect it to be a physical package failure. When i 
> monitor the output frequency, this seems to be indeed stable 
> up to my counter resolution of 1E-9 @ 1s. From that i induce 
> that the servo electronics in the FRK-L is working ok and 
> that it is indeed trying to correct for some VCXO instabilities. 
> 
> The big question however is: What makes the VCXO which has 
> been working very stable for years go in such a instable 
> behaviour from one day to another? Has anyone of you seen a 
> behaviour like this with a FRK-L? What way should i go for a 
> deeper diagnosis: Oscillator electronics or chrystal heater 
> electronics? 
> 
> Best regards and thanks in advance for any help.  
> 
> Ulrich Bangert
> df6jb at ulrich-bangert.de
>