Maybe they used a Cs standard for the original experimental units, but the first commercial Transit unit I saw (Magnavox MX700?) just had a big OCXO in it - it was also all controlled by a HP2100 computer and output the fix data onto a teletype.
The MX1102/1107 (which were pretty much standard equipment on big ships for years) used a rather smaller OCXO, and the MX4102 used a high-grade TCXO. Regards, Pete On Sun, Dec 18, 2011 at 10:30 AM, Brooke Clarke <[email protected]> wrote: > Hi Magnus: > > Exactly. The main problem with the Transit system was that the receiver > needed a Cs clock for the system to work at all. GPS removed that > requirement. > It's my understanding that a GPS receiver that uses a Cs clock has much more > capability. > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/Brooke4Congress.html > > > > Magnus Danielson wrote: >> >> Hi Jim, >> >> On 12/18/2011 01:25 AM, Jim Lux wrote: >>> >>> On 12/17/11 2:56 PM, Magnus Danielson wrote: >>>> >>>> On 12/17/2011 09:57 PM, Jim Lux wrote: >>>>> >>>>> >>>>> L1 C/A >>>>> >>>>> >>>>> But the real question isn't how to generate the signals (that's >>>>> straight >>>>> forward).. it's "how good does the oscillator have to be" to >>>>> effectively >>>>> test the receiver, in the sense of measuring it's timing performance. >>>> >>>> >>>> A decent OCXO should be able to pull it off. Your receiver should >>>> long-term follow your OCXO. Take one of these 40 dollar rubidiums if you >>>> are worried. >>>> >>>> Any drift of a good OCXO will be way within the bandwidth of the GPS >>>> channels. This drift would show up as added drift of the GPS oscillator, >>>> which is then being tracked and compensated. >>>> >>> >>> >>> that is precisely what I was thinking.. I was just wondering if anyone >>> had run across a reason why it wouldn't be the case. (short of actually >>> doing the no doubt tedious analysis) >> >> >> I can offer you several evidence of this: >> >> 1) None of the GPS simulators come with very special oscillator, but you >> may hook up your cesium if you need to for some reason. >> >> 2) A typical channel bandwidth typically measures in the Hz range. >> Tracking drift would not be too hard. >> >> 3) While we consider for all practical matter GPS time is stable and the >> GPS internal reference has incorrect frequency complete with drift, the GPS >> receiver uses the time-solution of the position to continuously correct the >> time, frequency and drift of the TCXO (or OCXO). Now, if we move a little of >> frequency error and drift over to the "GPS time" of the GPS simulator the >> receiver won't be able to say as long as the GPS simulator reference isn't >> drifting like a maniac so that the correction routines can't keep up with >> it. >> >> So, there is my rough analysis for you. >> >> Cheers, >> Magnus >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
