[time-nuts] Fury Interface Board: 5MHz needed?

[Didier Juges]

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Tom Van Baak
> Sent: Wednesday, November 07, 2007 3:05 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Fury Interface Board: 5MHz needed?
> 
...
> In a GPSDO the EFC is part of a closed loop. So even if there 
> is a small voltage offset in the EFC control or return path 
> due to heater current, it seems to me that it still has no 
> effect on either the accuracy or the stability of the GPSDO. 
> So we ignore that case too.

I believe the problem is that the EFC closed loop has a significant time
constant, so any current variation that is faster than the EFC loop time
constant will induce an uncorrectable error (at least as far as the EFC loop
is concerned). With a separate ground pin, or a circuit designed to
compensate for the effects of ground pin current, there will be no such
error.

Didier KO4BB