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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


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