[time-nuts] Have I wrecked my FE-5680A?

[Tom Van Baak]

Hi Bert,

I wish you the best solving the FEI bug. Not likely the factory will find and fix the bug and issue a service bulletin or offer f/w upgrades to us all.

It might be time work on a DDS-based, phase microstepper instead. See also the long thread:

https://www.febo.com/pipermail/time-nuts/2015-December/094982.html

With your AD9913 expertise, make a small board that takes some 5/10 MHz frequency as input and outputs 1PPS and 10 MHz shifted in phase and frequency as directed by a RS232/SPI port. Yes, it effectively replicates part of the circuitry in these FEI boxes, but if nothing else, that provides you with a reference design. Your f/w wouldn't have these kinds of bugs, and like the projects Nick does, it could be open source.

This board has many uses, not the least of which is a GPSDO. They key difference is that there is no need for Vref and DAC and EFC -- the disciplining is done at the ps level by the DDS slow phase / frequency shifter. Thus any oscillator can be used as the LO, not just ones with EFC input.

I agree it would be nice if the FE5690/50 and FE405 could be used they way you intend, but by doing your own DDS board your "universal GPSDO" would work on the widest range of oscillators possible -- from cheap TCXO to 5065A to cesium.

It would be a project of far greater present and future value to time nuts than a specialized, unreliable, closed source hack to a few old models of FEI parts. There must be enough RF and digital expertise on this list to pull it off.

/tvb

----- Original Message ----- 
From: "Bert Kehren via time-nuts" <time-nuts at febo.com>
To: <time-nuts at febo.com>
Sent: Friday, April 29, 2016 4:11 AM
Subject: Re: [time-nuts] Have I wrecked my FE-5680A?


Sadly yes
The reason we have not released our GPSDO for the FE5690/50 and FE405 is  
that we have experienced the same on all three devices. You are the 9th case  
that I know of. We know very little as to what exactly causes it but we are 
 incorporating circuitry to prevent it. What we know is that it is not a  
particular code sequence on the RS232 port, but what happens the operating 
code  is turning to mush. Some how the RS port is involved. Serious flaw on 
all  FE devices since most likely the code was written by the same individual.
Bert Kehren
 
 
In a message dated 4/28/2016 9:02:28 P.M. Eastern Daylight Time,  
time-nuts at febo.com writes:

Just as I  started testing the GPS discipline board prototype, my FE-5680A 
seems to have  developed a very odd problem.

If I give it power, it outputs a “kinda”  10 MHz sine wave while it sweeps 
around looking for a physics lock. This is as  expected.

About the time that I would expect the lock light to turn on,  instead the 
output just stops. The lock light never comes on.

This  unit’s been working fine for months now. It’s conceivable that I’ve 
sent it  some sort of serial command it couldn’t digest, but using the 
Windows  calibrator software seems to work - albeit there not being any output 
from the  oscillator at  all.


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