[time-nuts] UBlox GPSDO

Bob Camp kb8tq at n1k.org
Thu Apr 16 18:53:22 EDT 2015


Hi

How to phrase this … hmmm….

The 10 MHz you get off of these modules is “dithered” off of the 26 MHz TCXO. That’s not
really the best way to generate a clean signal. You can help that with some RF filtering. 

You also miss out on the long time constant narrow bandwidth filter that most GPSDO’s 
have in them. Without it you will pass a lot of very hard to filter noise. 

Since the 10MHz is not sawtooth corrected, it will have the same hanging bridge issues
as any uncorrected output. 

Low cost - certainly. High performance … not so much.

Bob

> On Apr 16, 2015, at 12:24 PM, Wayne Holder <wayne.holder at gmail.com> wrote:
> 
> According to page 51 of the protocol manual for the UBlox NEO-M* series GPS
> modules, the timepulse can be programmed to output a 10 MHz signal rather
> than a 1 PPS signal:
> 
> 
> http://www.u-blox.com/images/downloads/Product_Docs/u-bloxM8_ReceiverDescriptionProtocolSpec_(UBX-13003221)_Public.pdf
> 
> I'm curious if anyone has tried this.  Seems like a possible way to get an
> inexpensive GPSDO, as these modules are very inexpensive.
> 
> Wayne
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