[time-nuts] worth salvaging ?
paulswedb at gmail.com
Sat Jan 29 21:03:36 UTC 2011
On the 2201 I do give it quite a while to get its act together hours. To an
extent it seems to.
But the fact that the sat tables which you can view never seem to come into
alignment with whats going on for real is why I think it may be a lost
Back to odetics,
So it seems at least one works. Peter wouldn't you just keep it around or is
it sloppy compared to todays Tbolts and such?
Seems a shame to part'em out if they work unless they really aren't that
On Sat, Jan 29, 2011 at 1:14 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
> On Jan 29, 2011, at 6:43 AM, paul swed wrote:
> > It seems to interpret the almanacs wrong because amazingly enough its
> > actually does know the correct GPS week which was a shock to me. Unless
> > thats a simple calculation from the date I might guess.
> It's the other way around: The GPS week is directly decoded from the GPS
> signal. If I'm not mistaken, the GPS week roll-over causes a problem of
> being able to correctly calculate the calendar date from the GPS week. I
> could be mistaken, but I think that a receiver that doesn't handle the
> rollover properly but is otherwise in good shape should be able to track
> satellites and provide a correct position, but the calendar/clock time
> calculation would be wrong.
> In a receiver that doesn't have a recent almanac, and particularly in an
> older receiver that takes a very simple approach to downloading ephemeris
> and almanac information, initial acquisition could take a long time. It'll
> need to do a slow full-sky search for its first satellite, and older
> receivers couldn't do that nearly as quickly as newer ones can. Once it gets
> that first bird, it may sit there downloading ephemeris and almanac data for
> at least 12.5 minutes before it does anything else. With an old receiver
> from that era, give it at least a half hour of good open-sky conditions
> before you begin to suspect that it's dead.
> Back to the original topic now: That OCXO may seem mundane by time-nutty
> standards, but I'd certainly consider it to be worth salvaging. It could
> have all sorts of applications for radio stuff, portable test equipment, and
> even time-nutty stuff in an application that wants to be smaller and more
> portable than a Rb standard or full GPSDO.
> I also agree that there's likely to be a lot more salvageable stuff on
> those boards. I see lots of socketed parts. UV-erasable EPROMs are worth
> saving. Are those Altera parts reprogrammable? If so, then they're worth
> keeping. Keep any microcontrollers or CPUs that are reprogrammable, or rely
> on external program memory, or can still be used in spite of fixed internal
> programming (e.g., an old mask-programmed 8051 can be used as an 8031 by
> strapping a pin to tell it to ignore its mask ROM and use external program
> I'd say that any units which track satellites at all after a half hour
> should be considered for repair, and the rest of the units are goldmines of
> Mark J. Blair, NF6X <nf6x at nf6x.net>
> Web page: http://www.nf6x.net/
> GnuPG public key available from my web page.
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