[time-nuts] PN sequence generation using GPS

[Bob Camp]

Hi

Hop rates below 1,000 per second are far more common in simple systems than anything faster than that. At VHF, you are looking at a everybody being within one hop of each other. That makes the idea of a GPS based code start fairly reasonable. 

Bob


On Feb 23, 2011, at 5:03 AM, Hal Murray wrote:

> 
> albertson.chris at gmail.com said:
>> I think GPS can help by using it to control the transmitter and to set the
>> receiver frequencies but the "phase" of the frequency hop clock is
>> determined by the time of flight of the signal, something a receiver can't
>> know in advance 
> 
> Right.  But how big is the search space?
> 
> I think that depends on how fast you are hopping and the max distance you 
> consider reasonable.
> 
> A mile is 5000 ns or 5 microsecond.  If you hop every ms there are 200 miles 
> per slot.  If you hop every 100 ms there are 20,000 miles per slot.
> 
> If I pick a max distance of 1000 miles, that's 5 ms.
> 
> If you are off by half a slot, that will be 3dB down in the digital world.  
> It would probably be pretty ugly in the audio world, but it would be easy to 
> tune with a knob.
> 
> 
> Actually, you can know the distance in advance for some games.  Suppose I'm 
> going for the low power record from point X to point Y that are line of 
> sight.  ...
> 
> 
> -- 
> These are my opinions, not necessarily my employer's.  I hate spam.
> 
> 
> 
> 
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