[time-nuts] Re: HP Z3801A project update

[paul swed]

Ed what tool are you using to monitor the 3801.
LadyHeather remembers these bits of good stuff.
Regards
Paul.
WB8TSL

On Thu, Feb 24, 2022 at 2:46 PM ed breya <eb at telight.com> wrote:

> Last night I told it to do a survey, and let it slog through it
> overnight. This morning it seemed to be working fine, and apparently in
> position hold mode.
>
> Then I shut it down for about 45 min to let things cool down to nearly a
> fresh cold-start condition. On power up, it went through the usual power
> routine, and almost immediately began tracking satellites after the
> inner oven warmup, then within a few minutes, the GPS lock indicator
> came on. Also, before tracking even started, the position coordinates
> reported exactly the same as before power down. So, now this RX unit
> appears to be behaving "properly," just like the other.
>
> This RX unit was probably OK all along as it was, but I just didn't give
> it enough of a chance to catch up with everything. The question is why
> these two units, virtually identical, and neither having any long term
> memory, and operated in the same setup and location, would act so
> differently at first. There's no battery backup of the big SRAM, and I
> don't see any NVRAM evident. There are two big Flash RAMs, but I believe
> they only hold the firmware, so are not written to in normal operation.
> Maybe they are?
>
> I've been wondering where the actual, necessary data must be kept in
> order to get things working quickly like this. Since after a power down
> and up, the exact same location was recovered before any tracking was
> possible, it has to be stored somewhere in the RX or the Z3801A. I
> suppose the Z3801A could have some NVRAM - I haven't looked closely
> enough yet to see, but I will next time it's opened up.
>
> Now that this spare RX seems to be verified OK, my next experiment will
> be to swap them again and see how the original works first time up, with
> the Z3801A used to working with the spare. If it acts very slowly, then
> I'd surmise that the Z3801A treats it differently, because its ID number
> is different, and has to figure everything out again. If it still runs
> easy and quickly, then I'd have to think the data is in the RX, or that
> the Z3801A doesn't care, and it is the keeper of the data. If the latter
> though, then it's a mystery again - the Z3801A should have told the
> spare RX right away the location, quite accurately, and whatever else
> was necessary, so it should have been able to get up and go quickly,
> right from the first time.
>
> Ed
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