Hi Magnus:
Exactly. The main problem with the Transit system was that the receiver needed a Cs clock for the system to work at
all. GPS removed that requirement.
It's my understanding that a GPS receiver that uses a Cs clock has much more
capability.
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html
Magnus Danielson wrote:
Hi Jim,
On 12/18/2011 01:25 AM, Jim Lux wrote:
On 12/17/11 2:56 PM, Magnus Danielson wrote:
On 12/17/2011 09:57 PM, Jim Lux wrote:
L1 C/A
But the real question isn't how to generate the signals (that's straight
forward).. it's "how good does the oscillator have to be" to effectively
test the receiver, in the sense of measuring it's timing performance.
A decent OCXO should be able to pull it off. Your receiver should
long-term follow your OCXO. Take one of these 40 dollar rubidiums if you
are worried.
Any drift of a good OCXO will be way within the bandwidth of the GPS
channels. This drift would show up as added drift of the GPS oscillator,
which is then being tracked and compensated.
that is precisely what I was thinking.. I was just wondering if anyone
had run across a reason why it wouldn't be the case. (short of actually
doing the no doubt tedious analysis)
I can offer you several evidence of this:
1) None of the GPS simulators come with very special oscillator, but you may hook up your cesium if you need to for
some reason.
2) A typical channel bandwidth typically measures in the Hz range. Tracking
drift would not be too hard.
3) While we consider for all practical matter GPS time is stable and the GPS internal reference has incorrect
frequency complete with drift, the GPS receiver uses the time-solution of the position to continuously correct the
time, frequency and drift of the TCXO (or OCXO). Now, if we move a little of frequency error and drift over to the
"GPS time" of the GPS simulator the receiver won't be able to say as long as the GPS simulator reference isn't
drifting like a maniac so that the correction routines can't keep up with it.
So, there is my rough analysis for you.
Cheers,
Magnus
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