[time-nuts] EFC divider resistors

[Bob Stewart]

Hi Bob,

Do you think that maybe the oven current difference when the temperature changes could be at the root of this?  To me, it seems like this started when I put the divider in.  Before that, drift might have been hidden due to the lower resolution, I suppose.  In any case, Mouser has my money now, and we'll see what happens when better quality resistors are put in.

BTW, I'm feeding the pull-up divider with +5V from a 7805C bolted to the case.  I could switch that to the +6V  VRef from the OCXO if you think that would make any difference.  The case used to be an HP 37203A.




>________________________________
> From: Bob Camp <lists at rtty.us>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>Sent: Friday, January 31, 2014 3:50 PM
>Subject: Re: [time-nuts] EFC divider resistors
> 
>
>Hi
>
>If you are going to attenuate the EFC *and* center it up around 3V you will also need a voltage reference. Even a good one has a TC. You also have oven current running in the ground pin which contributes to voltage issues (oven and EFC share a common ground). Past that, you have thermocouple issues (resistors, wires, OCXO pins are different materials) ….
>
>Bob
>
>