Re: The birth of General Relativity


"cephalobus_alienus" <cephalobus_alienus.34a3606@xxxxxxxxxxxxxxxxx> wrote in
message news:cephalobus_alienus.34a3606@xxxxxxxxxxxxxxxxxxxx

Koobee Wublee;1257872 Wrote:
On Oct 23, 1:32 am, Jerry wrote:-
On Oct 23, 1:25 am, Koobee Wublee wrote:-
--
What actual GPS spec are you hallucinating about? Show me that
actual
spec as you have so gun-ho about it. shrug if not, shut the f*ck
up.-

Demanding to see "the specifications" is disingenuous of you,
because "the specifications" comprise literally thousands of
separate engineering documents, reports and memoranda (a) used by
the DoD to communicate high level and/or detailed requirements to
its major contractors (b) used by contractors to communicate
requirements to their subcontractors (c) used for internal
communications within a company or group (d) used for external
communications with end users concerning (e) general systems
development (f) specific systems specifications (g) interface
requirements.-

Calm down, dude. I just want to know where exactly in the
specifications that this 38uSec is specified in the GPS design. I
don?t think the ones claiming so can do so because they are all full
of sh*t.
-
Here is a link to one such specification, the Interface Control
Document:http://www.navcen.uscg.gov/pubs/gps/icd200/icd200cw1234.pdf-

Yes, indeed. It is so vague. Anyone working with actual specs would
call that an application note. shrug
-
See 3.3.1.1 Frequency Plan on page 11, 20.3.3.3.3 User Algorithms
for Subframe 1 Data pp 87-89, Figure 20-3 on page 92, 20.2.2.5.2.3
Almanac Time Parameters pp 121-122-

Where is that 38uSec crap again?

Page 11. Are you blind? Lazy?
No, you're being disingenuous again.

Concerning your use of the term "vague"...

As an INTERFACE Control Document, this specification specifies
requirements of the control interface that must be met. Actual
implementations are free to use whatever available hardware and
software solutions will satisfy the interface requirements.

Therefore the Interface Control Document does not recommend, for
instance, a choice between cesium or rubidium clocks. An
implementation could use a clock designed by Spaceman, if it
satisfied spec.

So long as the basic carrier frequency is displaced by a deltaF/F
of -4.4647x10^-10 from a nominal 10.23 MHz, the specification is
satisfied.

-----------------------------------------------------------------

Do you call it "vague" that an actual circuit diagram is not
provided that shows how this achieved? Well, I don't care to scan
and post on my web site the cat-peed and washed, wrinkled sheets
that I "inherited" from my brother (they still smell a bit),
photocopied from I don't know from exactly which engineering
document since they weren't removed from the ring binder when
they were copied and so are missing the inner edges, but here
goes:

The diagram describes a frequency synthesiser based on a phase
locked loop circuit that takes as input a cesium atomic reference
frequency (CARF) of 9.192631770 GHz, and used the CARF frequency
to lock a voltage controlled crystal oscillator (VCXO) to
precisely 10.229999995432 MHz. To do so, the CARF frequency is
divided by 530646691 and the VCXO frequency is divided by
590529 for a common frequency of 17.32345066107 Hz. A phase
comparator circuit monitors any phase difference between the
17.32345066107 Hz signals from the CARF and the VCXO, and adjusts
the voltage applied to the VCXO so as to maintain a zero phase
difference between the two frequency sources.

In this manner, the VCXO is locked to a precise 10.229999995432
MHz output frequency that represents 10.23 MHz modified by a
relativistic correction.

Is THIS the sort of level of detail that you need? Then you are
being ridiculous, since the circuit diagram specifies ONE SINGLE
IMPLEMENTATION of what must have been lifted off in an early
satellite, since it shows a lot of discrete components whereas
nowadays most of the discrete components would probably go into
a single ASIC.

IT IS NOT THE FUNCTION OF THE INTERFACE CONTROL DOCUMENT TO GO
INTO THE LEVEL OF HARDWARE/SOFTWARE DETAIL THAT YOU SEEM TO
DEMAND OF A "SPECIFICATION".

Implementations change dramatically as the level of technology
improves. The interface requirements have remained relatively
constant, except that additional functionality has been added
reflecting the added capabilities of the more recent series of
satellites.

Jerry

Doesn't mean diddly squat, the tolerance (error bound) of GPS is
+/- 90 feet vertical.

Don't rely on it to land a plane, Major Crank.





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