[time-nuts] Frequency Dividers

Randy Warner Randy at synergy-gps.com
Tue Aug 8 17:42:24 EDT 2006


John,

I totally understand the concerns about stability. In the experiments I
have run the jitter is down in the ps range. Temp would be a whole other
animal. I have just been running these in the lab. Oh well, it's all
fun.

Randy 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Ackermann N8UR
Sent: Tuesday, August 08, 2006 2:31 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Frequency Dividers

Randy Warner said the following on 08/08/2006 03:23 PM:

> I have been seeing a lot of traffic concerning making 10MHz frequency 
> dividers using PIC's. While they provide an elegant solution to 
> providing an accurate 1PPS from a precision source, I have to ask if 
> there is a reason for going this route? I am just using three HCT40103

> down counters hooked to a DS4000 to get what I think is a very stable 
> 1PPS. Am I missing something? I realize 40103's are as old as dirt (I 
> guess I am showing my 4000 series CMOS days), but the HCT series have 
> plenty of bandwidth.

Hi Randy --

I think the concern in using the older discrete devices is their
potential for jitter in general, and temperature sensitivity on top of
that.  But I've never done any experiments on just how big a problem
those issues are.

John

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