[time-nuts] Checking the Frequency of a Rubidium Oscillator
brooke at pacific.net
Tue Nov 11 19:12:21 UTC 2008
It's my understanding that if you look at the signal from a common GPS antenna
and feed it into a spectrum analyzer you will not see the signal. My guess is
that when developed by the military it was designed to be a stealth system.
GPS is what's called a Spread spectrum signal.
Also the best possible s/n radio is determined by how orthogonal the different
PN codes are to each other. These are described in ICD-GPS-200 which is on
along with other GPS info.
Here's a National Instruments page about GPS signal generation:
The definitions on this page for the various Time To First Fix flavors may not
Brucekareen at aol.com wrote:
> I have an EIP Model 548 counter with a YIG-tuned front end that can be
> programmed to scan over narrow frequency ranges. By feeding the rubidium
> oscillator under test into the 10 MHz clock input of the counter, is there any
> reasonably simple way to directly measure the frequency of a GPS satellite
> transmission so as to ascertain the accuracy of the rubidium source? The counter has
> an input sensitivity in the order of about –25 dBm -- not sufficient to
> measure directly from an amplified antenna, but perhaps through an amplifier. I
> am not sure whether the input YIG tuner selectivity is sufficient to separate
> transmissions from the various satellite’s (or are they TDMS?). What do you
> Bruce, KG6OJI
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