[time-nuts] Trimble Resolution SMT - good/bad/indifferent?

[Jim Lux]

On 5/11/12 2:38 AM, Hal Murray wrote:
>
>> Why in the hell would anybody build a 50 channel receiver?  At most you
>> MIGHT see 12 usable GPS sats...  I don't think that I've seen over 10.  WAAS
>> should be fairly useless for a timing receiver.
>
> I can think of a couple of reasons.  I'm sure there are more.
>
> One would be marketing type bragging rights.  I can scan more channels than
> you.
>
> Another area would be cold-start time.  If you have to search N slots, more
> searchers runing in parallel is likely to speed things up.
>
>
Searchers and trackers are often different logic, these days..

Searching is very efficiently done with a FFT correlator, because you 
can search all lags simultaneously with NlogN effort as opposed to 
O(N/2) effort with a sequential search.  Same for Doppler.

But once you've acquired, you track with a conventional 
Early/Prompt/Late scheme.

When you get into full-up implementations, where there is coupling 
between the tracking loops (think of a 2 frequency receiver.. L1 and L5 
will have related doppler), there are other "economies of scale" possible.