[time-nuts] GPSDO vs Rb standard

Bob Camp lists at rtty.us
Wed Sep 18 20:43:02 EDT 2013


Hi

There are lots of case solutions. A busted piece of HP gear is a nice way to come up with a case. Heatsink material is available from several web sites cut to order quite cheap. A simple computer fan is way more air than you will ever need. The obvious missing link is the controller. I'd run something up with a micro talking to a 4 wire fan header. That way you have tach feedback on the fan and all the PWM stuff is driven on the fan end. More or less a weekend project on a piece of pert board. Maybe a bit more than that if you do a pc board. 

(yes I realize this heading horribly close to talking about building things …. alarm bells are ringing somewhere…..)

Bob

On Sep 18, 2013, at 8:32 PM, Bob Stewart <bob at evoria.net> wrote:

> Bob, I've been mulling over the question of a case, and I was thinking of getting a 2M brick amp and putting it inside, bolted upside down to the heat sink.  Good idea?  Anybody got a busted one?
> 
> Bob
> 
> 
> 
> 
> 
>> ________________________________
>> From: Bob Camp <lists at rtty.us>
>> To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
>> Sent: Wednesday, September 18, 2013 7:22 PM
>> Subject: Re: [time-nuts] GPSDO vs Rb standard
>> 
>> 
>> Hi
>> 
>> The Rb's have a couple of issues:
>> 
>> 1) Its been years since they were set on frequency and they do have a yearly drift rate
>> 2) They have a temperature coefficient of drift that may be fairly large (0.1 ppb over -30 to +70)
>> 3) They self heat quite a bit, so they do move temperature / need a heatsink
>> 
>> The solution to the temperature issue is a servo controlled fan. The solution to the first drift / accuracy issue is to calibrate them against something else.
>> 
>> Bob
>> 
>> 
>> On Sep 18, 2013, at 7:13 PM, "John C. Westmoreland, P.E." <john at westmorelandengineering.com> wrote:
>> 
>>> Azelio and Fellow Time Nuts,
>>> 
>>> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>>> imagine this is in the specs of the specific receiver -
>>> but I was wondering if some of you have actually measured what that is -
>>> and could report the numbers that you have found.
>>> 
>>> Thanks!
>>> John Westmoreland
>>> 
>>> 
>>> 
>>> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani <azelio.boriani at screen.it>wrote:
>>> 
>>>> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
>>>> will find out that the Rb is slow... you can also check the Rb's PPS
>>>> against the GPS's PPS.
>>>> 
>>>> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart <bob at evoria.net> wrote:
>>>>> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
>>>>> GPSDO to Channel A, .05us trace, and turned the lights out so I could
>>>>> see it.  The 10MHz is marching right to left about 1 cycle every 20
>>>>> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
>>>> about 5ppb?
>>>>> 
>>>>> 
>>>>> Bob
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
>> 
>> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list