[time-nuts] Chooses for a desktop/server NTP external 1PPS reference

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Dec 7 23:07:17 UTC 2009


Alexander Sack wrote:
> On Mon, Dec 7, 2009 at 5:20 PM, Bruce Griffiths
> <bruce.griffiths at xtra.co.nz>  wrote:
>    
>> Alexander Sack wrote:
>>      
>>> Hi Everybody:
>>>
>>> First post, be gentle.  I did some mail-list archive searching and it
>>> seems
>>> that a lot of folks have used the Garmin 18x LVC as their 1PPS sync for
>>> the
>>> desktop with varied success (5V via USB port and RS-232 for 1PPS?).  At
>>> work, I have experience with an Endrun Cf/Ct receiver connected to a small
>>> CDMA antennae (as well as GPS receiver) which works pretty well (I suppose
>>> its more relative to my crappy motherboard oscillator than anything).  I
>>> have no idea how much they run (I think the CDMA one was like $200 and
>>> something).
>>>
>>> What are my options in this realm?  Surprisingly enough, Googling for over
>>> an hour didn't yield much results.  There are tons of companies that offer
>>> various solutions but with little pricing information.  I'd be happy to
>>> hear
>>> some suggestions OTHER THAN the Garmin 18x LVC?
>>>
>>> (btw is there such a thing as a desktop rubidium atomic clock with 1 PPS?)
>>>
>>> Thanks!
>>>
>>> -aps
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>>>
>>>        
>> A Soekris 4501 running nanobsd using an M12+T or M12M GPS timing receiver
>> works very well.
>> Failing that an M12+T or M12M GPS timing receiver also works well with a
>> desktop machine that runs FreeBSD.
>>      
> Yeah I'm running FBSD (actually that's my day job).  What's the
> M12+T/M12M, is that a Motorola substance?  Linky-link?
>
> -aps
>
>
>    
The M12+T is a Motorola GPS timing receiver (can be picked up on ebay) 
but requires an CMOS- to RS232 transceiver chip and a few other parts as 
well as an active GPS antenna.
The iLotus M12M is the replacement and can be purchased from Synergy GPS 
complete with a suitable motherboard and puck style antenna.
A GPS timing antenna (eg VIC100) with integral 1575MHz bandpass filters 
is more resistant to interference.

http://www.synergy-gps.com/index.php?option=com_content&task=blogcategory&id=32&Itemid=116 
<http://www.synergy-gps.com/index.php?option=com_content&task=blogcategory&id=32&Itemid=116>

for the M12M timing starter kit which has everything needed to get you 
started.
later depending on your location you may want to upgrade to a timing 
antenna:

http://www.synergy-gps.com/index2.php?option=com_content&do_pdf=1&id=139 
<http://www.synergy-gps.com/index2.php?option=com_content&do_pdf=1&id=139>

I have an M12+T currently serving as the ref clock for a Soekris4501 ntp 
server (runs nanobsd generated from FreeBSD 7.20 I am about to upgrade 
to a version derived from FreeBSD 8.0 ).
It has previously been used as the ref clock for an old desktop Pentium 
ntp server running FreeBSD 6.0

Bruce




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