[time-nuts] Determination of the placement of the first pps

J. L. Trantham jltran at att.net
Wed Jan 25 22:13:52 EST 2012


I went back to the shop tonight and checked both my FE-5680A's.

Both pin 3 and pin 6 are 'high' when power is first applied.  When the unit
'locks', both pin 3 and 6 go 'low' but pin 6 then puts out a 5 uSec wide 1
PPS pulse, as judged by my 'calibrated eyeball' which means that I used a
stop watch and counted the time for 10 sweeps of my scope, triggered by pin
6 and set for 5 mSec/cm sweep.  These are, indeed '1 pulse per second'

Now, I need to move the power supplies, scope and FE-5680A to where my 5370B
and TBolt are located.  Don't hold your breath on that though, too many
irons in the fire.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Magnus Danielson
Sent: Wednesday, January 25, 2012 1:19 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Determination of the placement of the first pps

Hi Joe,

On 01/25/2012 08:04 PM, J. L. Trantham wrote:
> Magnus,
> Thanks for the research.  Now that I have read your information, I am
> to have to go back and 'measure' the PPS output on my unit.  I just
> 'eyeballed' the '1 PPS' and it seemed close to 1 second.

Good luck. Hopefully I put you onto a working solution.

> It would be nice to find a serial command that would allow placing the 1
> at any arbitrary point in phase to match GPS.
> My impression of reading the posts about the FE-5680A is that the 1 PPS is
> likely there, just not easily documented.

Well, being lazy enough not to go into the lab and open up my 5680 I 
went hunting the web and it seems like there was more out there than we 
seems to have been piecing together.

Seems like a bit of more systematic research needs to be done. There are 
obviously at least two basic models, one older with 50,255+ MHz 
oscillators and various add-on boards and secondly the 60 MHz + DDS 
variant. Reverse-engineering the schematics and functions has only 
partly been done, but I haven't seen any systematic schematic popping 
out of the work.

There is already plenty of information available, but it is not 
coordinated and systematically done to the level that most aspects can 
be written down in a service type of document.


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