#Garmin homeport nmea gps input code#

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. I warmed my module and could get a much higher ripple after the RC-filter (In other modules cooling may give the same increase instead).Ĭommercial module - 0.1 parts per billion per day. If it is exact it could give a sawtooth that moves the output. One thing with the 1MHz giving so low ripple after the RC-filter I believe is due to the GPS TCXO '48Mhz' is not exact. If the OCXO is better than the GPS at the time constant chosen it will limit the performance (but still work well). My guess is that you may get an ADEV from the GPS 1MHz (after the RC-filter) that is around 1E-9 for 1sec, 1E-10 for 10secs and 1E-11 for 100secs. These need to be read in context in the article referenced above. User lars makes the following comments on achieved stability/accuracy. Here is a writeup of the EEVblog community, based on his initial test here. The relevant output is timepulse2 / pin 9 on the LEA-6T. The sheer volume of these base station applications has profoundly affected the OCXO market by driving prices down and consolidating vendors.Īs of 2023 the GPS involved for this solution is obsolete.Ī more than adequate GPS replacement is the ublox LEA-6T which has a user programmable frequency output driven by a divider from the modules internal 32 MHz oscillator which in turn is GPS synchronised.

#Garmin homeport nmea gps input 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 Hz 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.

Long term the 1 Hz signal is probably the most accurate time, and so also frequency, reference that you will ever encounter. This is already showing signs of being replaced, but the features it has that make it ideal should also be in newer modules. So, I've added a well documented DIY solution using the available-in-2023 UBlox LEA-6T. The GPS module used to make the 'super simple disciplined oscillator' mentioned below seems to be no longer available, although it might be found on the surplus market.