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Re: U2 gps timing data

Tony Volpe #1475 Thanks for the explanation Hans. If you say it, it must be true. The reason I sound puzzled is that when I started having trouble with the U2 and my GPS board, and since I don't have a scope, I rigged up a way of listening for the GPS board's 1pps with an earphone. I watched the behaviour, or listened to it on the 1pps line. When the unit had no lock, all was silent, then as it got lock, the red led on the gps unit began flashing and about eight seconds later, I started to hear a tick in the earphone as the GPS began sending the 1pps. You must be right and it keeps sending even if there is no lock, but I didn't think so. When I get the chance, I'll set up my 'ear scope' again and see. :)) Tony toggle quoted message Show quoted text On 1 July 2013 14:53, Hans Summers <hans.summers@...> wrote: ? Andy: When GPS is ON, the U2 relies on the 1pps as it's one second tick. The U1 behaved exactly the same way. If you have a GPS module which stops sending the 1pps signal when it loses satellite lock, then the U2 time would stop too. Tony: Some GPS modules stop the 1pps signal when the satellites lose lock. If you have that kind, the U2 would stop then too. The U1 behaved the same. If your GPS module lost lock then I think it must be the kind which still sends a 1pps signal regardless (from the GPS module's internal timing). Andy:? If your U2 jumps 1's and 2's seconds when not in GPS mode then I think you have some other problem, RF pickup, ground loops, I have no idea... but that definitely isn't normal! The U2 should be able to operate correctly with no GPS module and should be accurate enough once you calibrate the system clock, for many days of WSPR operation. All: You are all correct though: I should make the software so that if the 1pps signal stops for any reason, the system keeps time with its own internal oscillator, the same way as when GPS is off. One more enhancement for the list :-/ 73 Hans G0UPL On Mon, Jul 1, 2013 at 2:32 PM, Andy Cutland <gj7rwt@...> wrote: ? Hi Tony, I've only switched the U2 off gps once to check the 20mhz clock setting anf the results scared me so I switched the gps back in straight away. The seconds were very random, jumping up in twos and stopping then jumping again? I guess this may be the problem then ! 73's De andy From: Tony Volpe <tony.volpe.1951@...> To: QRPLabs@... Sent: Monday, July 1, 2013 1:05 PM Subject: [QRPLabs] Re: U2 gps timing data ? How far out is the nominal 20MHZ clock setting from the actual oscillator frequency Andy? I can't see how the unit could go off time over a few minutes? My understanding is that it resorts to its own internal clock if the GPS loses lock. My UQ1 certainly did that. I have often observed the GPS board losing lock in my year long 24/7 operation of the UQ1. It might ?lose the satellites for ten minutes at a time (being indoors) and then regain it. Its time keeping remained well within bounds throughout its operation. Even with the system clock being set at the nominal value, the unit ought to keep time for many hours without getting outside the WSPR time parameters.? Tony G0BZB

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#1475

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