[time-nuts] 5 MHZ PIC PPS Divider?

Stanley Reynolds stanley_reynolds at yahoo.com
Tue Apr 15 17:19:28 EDT 2008

Thanks Pete not sure my wife will let another big box in the door. I was thinking of some thing like this :
a ECL 8-Bit Ripple Counter. And a 1Ghz oscillator make the measurement of  differences. This should get me to the 1ns level ?
But looking at the sampling heads may be close to what I want, I will look for some manuals on the web. I would want to transfer the data to a PC, would I need a GPIB Interface and some software ? I'm trying to eliminate the extra stuff like the scope tube and it's power supply and end up with a small box to interface to the computer.

----- Original Message ----
From: Pete <peterawson at earthlink.net>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Tuesday, April 15, 2008 3:13:02 PM
Subject: Re: [time-nuts] 5 MHZ PIC PPS Divider?


Jitter measurements of moderately high frequency
sources can be made directly with relatively cheap
used instruments.

Older sampling 'scopes from H-P and TEK appear
on *Bay frequently. The H-P 54120 family boxes
are down to US$500 to 800 with sampling heads 
capable of 12.4GHz measurements. These show up
about once per month. If you're trying to buy one,
wait for a complete system (mainframe+sampling 
head) which is listed as operational & you have
confidence it's actually working. These things are
HEAVY & having to return a junker is painful;
even if you get your money back.

These mainframes have jitter capture & analysis
built in. The internal trigger jitter floor is about 1ps,
good enough for most measurements. The internal
timebase delay feature allows measuring multi-
cycle jitter out to many screens width of data.
Obviously, long delays will introduce added
jitter floor contribution, but it's still quite good.

Pete Rawson

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