[time-nuts] Pulsars make a GPS for the cosmos

[Jim Lux]

On 9/28/13 7:32 AM, Hal Murray wrote:
>
> jimlux at earthlink.net said:
>> Scrolling down, it looks like they're getting a whopping 0.5 dB SNR on
>> the Crab Nebula pulsar.
>
> How much of the noise comes from local sources vs thermal or galactic?
>

These are amateurs, so they're probably not using cryocooled receivers: 
a good part of the noise is kTB noise in the receiver.

>
> I'm missing the scale factor for the big picture.  How big a volume does this
> work over before I have to start counting fringes or something like that?
> Wiki says the longest one is 8.5 seconds.  That's small even on the scale of
> the Solar system.

You also get direction, so for a "navigation" system, you can figure out 
where you are.

Time wise, you'd have to count ticks.

>
> Is there some trick I'm missing?  Are there lots and lots of pulsars at
> different frequencies so I can beat them against each other to make larger
> synthetic fringes?
>
> Are X-ray or gamma-ray pulsars (much) slower?
>
>