Volumes of books on standards define these rules.Īll of the existing answers talk about precision timing applications I just want to point out that the 1 pps signal is important for navigation, too - particularly when the receiver is moving. Of course that takes uber diligence in the design of your DO. Networks use intelligent error logging for ranking references of Stratum clock sources. Telecom synchronous high speed networks depend on precise clocks as do licensed radios. Redundancy is key for reliability if you have choice and ranking of sources from Stratum 1,2,& 3 clocks in case of outage. Note that a cycle skip in phase error could be N cycles which means ambiguity of accumulated error. So with 1 PPS (1Hz) clock you can support a large range and time interval without cycle skips or counts on precise phase difference. The frequency error represents velocity as in radar speed. The range for vehicle travel is simply the phase difference using the difference frequency and phase of the telemetry sub-carrier and the ground station at the chosen f with Δλ=c/f with Δposition=Δλ + cycle counts. In my OCXO I chose 10MHz for the OCXO, 100KHz for the rocket's FM sub-carrier telemetry and 10KHz for the mixer ground station to track the rocket's position.
So care to minimize drift and phase noise is essential. When you multiply f by N by PLL divider you also multiply phase error. The importance of stability depends on outages and how much error you can tolerate during outage or LOS (loss of signal) as well as capture time. actually after only 1st GPS (GOES 1) was launched, it brings back fond memories. Having designed ruggedized OCXO for harsh rocket environments and tracking floating weather stations before GPS. The sheer volume of these base station applications has profoundly affected the OCXO market by driving prices down and consolidating vendors.Ĭommercial module - 0.1 parts per billion per day.
#Utc time vs gps time code
They are also widely deployed as GPS time and frequency references for the base stations operating under the IS-95 standard for the Code Division Multiple Access (CDMA) cellular mobile phone systems originated by Qualcomm. GPS-disciplined DOCXOs are the Stratum I Primary Reference Sources (PRS) for many of the world's wired telecommunications systems. In this way they may be "disciplined" to match the frequency of a GPS or Loran-C reference receiver. Such oscillators are used in laboratory and communications grade applications and often have the means to adjust their output frequency via electronic frequency control. When a single (OCXO) or double (DOCXO) temperature-controlling oven is wrapped around the crystal and its oscillating circuitry, the frequency stability may be improved two to four orders of magnitude relative to that of the TCXO.
A DO is not frequency locked per se but is gently kicked into lock by error signals between a 1 H signal generated by local and GPS clocks. You can buy commercial "disciplined oscillator" units and designs for DIY ones are available. You are effectively obtaining something like a cesium clock time reference for the cost of a GPS module. So there should be no 1 hour difference.Long term the 1 Hz signal is probably the most accurate time, and so also frequency, reference that you will ever encounter.
The minute discrepancy is due to when I took the screen shots 1 minute apart.Īny ideas why there is a 1 hour time difference? I've tried setting Daylight Savings time on, since we're currently in daylight savings time, but then KStars updates to 17:44, and is two hours off. You can see the time is 15:44 on the mount, and 16:43 in KStars. In KStars, when it syncs, it shows the time +1 hour even though it shows there is no offset, and location and time have updated. This should show UTC correctly without any offset, and on the hand controller it does. Local Timezone is set to 0, and Daylight Savings is set to OFF. On the mount hand control, UTC is correctly displayed for date and time. I use a GPS to obtain Date and time on the Mount. When I connect, it syncs the date and time, but UTC is off by one hour. In settings, I have it set to obtain date and time from the mount.
#Utc time vs gps time update
I'm having some issues with getting KStars to update to the proper time from the mount.
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