[time-nuts] Ublox F9P multi-band GPS receiver

[Bob kb8tq]

Hi

On a “chip" based setup like this, it’s a matter of pulling the TCXO and putting in some
wires. Whatever frequency the TCXO used to supply, that’s what your magic external 
device needs to provide. The designers do not seem to allow you to provide a variety
of input frequencies. Given how the input gets used for all sorts of things, that’s not
as crazy as it sounds.

The option to pull the TCXO and fiddle has been there for quite a while. At some point
they will move the TCXO function inside the “chip" package (with MEMS or some other 
magic). Once they do, the ability to tear it off will become a bit more difficult…. :)

Once you do replace the TCXO, you then are very dependent on a sawtooth correction 
to run your GPSDO. The PPS becomes one big long hanging bridge and thus is not useful. 
Carrier phase or (like in the TBolt) code phase data could be used as an alternative to 
a sawtooth correction word. 

There also are some pesky issues about frequency slew rates and other nonsense you
could bump into doing a TCXO replacement.  I can’t think of any that would be terribly
hard to take care of. That all assumes you have a good clean reference. 

Bob

> On Jan 22, 2019, at 8:10 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> 
>> The one thing which is missing is a external frequency input. You can 
>> get a frequency output in its place, but it does not fully replace the 
>> input. That's where the module vs. chip comes in.
> 
> Consider talking to sparkfun about how they should do the next version ?
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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