[time-nuts] GPS Timing Source -- looking at buying

Bob Camp lists at rtty.us
Mon Jul 12 08:15:49 EDT 2010


Hi

The original post simply mentioned EBU. Thus the confusion.


Bob



On Jul 11, 2010, at 8:23 AM, "Ed, k1ggi" <k1ggi at comcast.net> wrote:

> Keep in mind, SMPTE/EBU is timecode, AES/EBU is digital audio.
> 3 orders of magnitude difference in the bit rates.
> Chris was talking timecode.
> Ed
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Bob Camp
> Sent: Friday, July 09, 2010 8:38 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS Timing Source -- looking at buying
> 
> Hi
> 
> The Thunderbolt has a GPS and an OCXO inside it. It's built in smarts align
> a PPS created from the OCXO to the GPS PPS. This allows the PPS to be more
> stable than a normal GPS PPS (less jitter). It also provides holdover on the
> PPS if and when GPS sat's are not available. 
> 
> Since your ultimate objective is (I think) AES / EBU timing, jitter is an
> important consideration.
> 
> Bob
> 
> 
> On Jul 9, 2010, at 3:10 AM, Chris H wrote:
> 
>> I might go for the Garmin one to start with, and see how it all works..
>> and then move up to a more reliable source of timing source in the
>> future...
>> 
>> When you say Reliable, what exactly do you all mean---
>> does it loose time? 
>> Does it loose lock to the satellites?
>> because it's only millisecond accurate, is that your concerns....
>> 
>> Please correct me if I am wrong: 
>> 
>> If it's pulsing every second, and that second is generated by the lock
>> to the satellite, then should it not be as accurate as the device that
>> it's getting it's lock from?
>> 
>> (Sorry I am new to all this)
>> 
>> 
>> On Fri, 2010-07-09 at 19:02 +1200, Chris H wrote:
>>> Yes sorry -- stratum 1 -- brain fart :(
>>> 
>>> 
>>> 
>>> On Fri, 2010-07-09 at 06:32 +0000, Paul Nicholson wrote:
>>>> Chris H wrote:
>>>>> Would be good as a timing source for GPS
>>>>> ... make a PC into a Stratum 0 timing device?
>>>> 
>>>> I think it would count as stratum 1, since you are 1 hop
>>>> away from a master time source.
>>>> 
>>>> This page may be of interest,
>>>> 
>>>> http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm
>>>> 
>>>> Trimble Thunderbolts have been recommended on this list as a
>>>> proper timing grade GPS, superior to these EOM Garmin GPS units.
>>>> 
>>>> There's a reliable source of Thunderbolts on E-bay.  I currently
>>>> have one of these on order,
>>>> 
>>>> http://cgi.ebay.co.uk/290322053618
>>>> --
>>>> Paul Nicholson
>>>> --
>>>> 
>>>> 
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>>> 
>>> 
>>> 
>>> 
>>> 
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>> 
>> 
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