[time-nuts] Building a GPSDO & trouble using Jupiter-T

Azelio Boriani azelio.boriani at screen.it
Fri Feb 3 10:52:18 UTC 2012


I have implemented a digital lock detector in my CPLD timing the phase
detector itself. It was years ago... let me find the VHDL code so that can
give any idea how to implement it for a microprocessor.

On Fri, Feb 3, 2012 at 10:58 AM, Roberto Barrios <rbarrioss at msn.com> wrote:

> Long time ago I built a Jupiter-T companion board that included the loop
> filter, divider and phase detector for the James Miller GPSDO. It also
> includes a PIC that monitors the NMEA strings and displays different status
> data via LEDs, and outputs data via RS232.
>
> http://www.rbarrios.com/**projects/10KGPSDO/<http://www.rbarrios.com/projects/10KGPSDO/>
>
> I used an ISOTEMP OCXO and it worked well.I also tried to implement a lock
> detection mechanism, first based on timing the phase detector and sencondly
> monitoring the swings of the EFC. I was not very happy with any of those
> solutions and finally gave up. Details are in the code.
>
> Text is in spanish but you really don't need to read it, it is very, very
> basic for you time-nuts. If anyone has a suggestion for a better lock
> detection solution applicable here, I'd love to know about it.
>
> Best regards,
> Roberto EB4EQA
>
> -----Mensaje original----- From: Tom Van Baak
> Sent: Thursday, February 02, 2012 11:56 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T
>
>  This thread got started when someone asked if an analog PLL would work
>> for building a GSPDO.  For that you do need timing pulses much faster
>> then 1PPS.
>>
>> But the analog PLL are not the way to go for best accuracy.
>>
>
> Remarkably, the simplest and still one of the best GPSDO I've
> tested was the 10 kHz Jupiter and analog PLL-based standard
> by James Miller. It performed superbly. It's the 4th GPSDO at:
> http://www.leapsecond.com/**pages/gpsdo/<http://www.leapsecond.com/pages/gpsdo/>
>
> True, there exist some better GPSDO, and you need digital if
> you want a hold-over feature, but I wouldn't discourage anyone
> from trying the analog PLL method. The sheer simplicity might
> more than make up for a few less ns. Miller's page is at:
> http://www.jrmiller.demon.co.**uk/projects/ministd/frqstd.htm<http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm>
> http://www.jrmiller.demon.co.**uk/projects/ministd/frqstd0.**htm<http://www.jrmiller.demon.co.uk/projects/ministd/frqstd0.htm>
>
> /tvb
>
>
>
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