[time-nuts] how good an oscillator do you need for a GPS simulator

Azelio Boriani azelio.boriani at screen.it
Sat Dec 17 09:58:39 EST 2011


Correct: I was thinking how to simulate an only bird. The RACAL GPS101 is a
single channel simulator and maybe made that way. Then it is possible to
place a number of 1 channel simulators at a distance...

On Sat, Dec 17, 2011 at 3:18 PM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:

> On 12/17/2011 02:37 PM, Azelio Boriani wrote:
>
>> Jim, you're right a DAC is not needed: I was thinking of generating the
>> BPSK by a DAC but it is not necessary. I have seen some BPSK hardware
>> modulators: easier than generating samples and feeding a DAC.
>>
>
> For a single bird a digital output could be made to work, but for a
> constellation you would need individual bits which would then be mixed
> together using a resistor network since the birds will not have the same
> information due to different PN-cods, same rate since they will have
> different doppler rates etc. etc. Having a three or four bit DAC would be
> an alternative. Also, the square carrier waves would require more filtering
> than what a few-bit sine would require.
>
> So, saving a DAC is not necesserilly as smart as it looks.
>
> Looks like there is room for a GPS/GNSS receiver and simulator list.
>
> Cheers,
> Magnus
>
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