[time-nuts] Ublox time/freq aiding was Re: Linear voltage regulator hints...

[Simon Marsh]

On 14/12/2014 04:08, dan at irtelemetrics.com wrote:
>  > Note that most high-end GNSS timing receivers go one better and 
> simply have an external input for the clock. That way you feed your 
> own lab clock into the receiver. If you have Rb/Cs/maser you would use 
> that as the reference. It's what the national timing labs do, along 
> with dual-frequency and post-processing and all the other tricks of 
> the trade.

>  I think it would be agreat idea also. It's a wonder that more of the 
> 'timing' receivers don't have that external clock option! I wonder 
> what these Ublox parts use for a clock? Is it something frequency 
> compatible with a 10Mhz source??? (Hmm, can we pry one apart to figure 
> it out! ;) ) 

Ublox modules have a 48mhz internal clock.

There is the following interesting paragraph in at least the 7 & 8 data 
sheets:

---

1.8.2 Aiding
The EXTINT pin can be used to supply time or frequency aiding data to 
the receiver.

For time aiding, hardware time synchronization can be achieved by 
connecting an accurate time pulse to the EXTINT pin.

Frequency aiding can be implemented by connecting a periodic rectangular 
signal with a frequency up to 500 kHz and arbitrary duty cycle (low/high 
phase duration must not be shorter than 50 ns) to the EXTINT pin. 
Provide the applied frequency value to the receiver using UBX messages.

---

I haven't been able to find any information about what this actually 
does though. Anyone know ?

Cheers


Simon