Re: NEO series GPS modules

Neil Smith G4DBN

Andy, when you say"very" narrow loop bandwidth, are we talking time constants of tens of seconds, or even longer? 

I'm with you totally on the Rubidium front, I now run an Efratom Rb source as the primary standard, and just use my G3RUH GPSDO for verification.  I also use a couple of Morions for /P, but I would like to lock them to GPS just for the sheer hell of it.  No real justification for doing it, perhaps I'm turning into a time-geek.

Neil G4DBN

On 26/07/2016 17:16, Andy Talbot andy.g4jnt@... [ukmicrowaves] wrote:
Instead of this rush for GPSDO based references with dubious short term stability, why not go for one of the several really good 10MHz OCXOs that have appeared recently or even a Rubidium source.   There are several Morion types out there, all capable of resetting to within a few parts per billion after a quite rapid warm up.

I have one in the 10GHz PortaBeacon that settles within a couple of tens of Hz (at 10GHz) within 5 minutes of switch on from cold - always.  And that module is an older generation OCXO  - later ones are better still.

Then use a basic GPS module with its 1 PPS output as the reference just for a frequency counter to confirm your calibration from time to time.

Best of all, get a Rubidium source - there are a few around on Ebay for £100 or so.   Not the cheapest option, but that will guarantee you sub PPB accuracy within less than 20 minutes of turn on.  

GPSDOs may be cheap, and although I've never tried these GPS modules being talked bout here, do get an uncomfortable feeling that unless used with a very narrow loop bandwidth locking up a reference, they won't be all that nice when multiplied up to the higher uWave bands.

Unless someone knows better, and has done so ?

Andy  G4JNT


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