[time-nuts] New timing receivers?

Bob Camp lists at rtty.us
Sun Apr 27 11:04:34 EDT 2014


There are an enormous lot of variables when you do all of this. You also need to figure out what you are really looking for. Often that relates to system specs. 

A WAAS enabled receiver will probably give you a better fast survey than a simple receiver. Are you doing a >48 hour survey or a <1 hour survey?

Do you care about UTC offset? Are you just looking at second to second deltas? 

Are you comparing an ensemble of like receivers to each other? 

How good is your reference at various offsets? 

How good is your sky view? How nasty is the space weather this week / month? 

What kind of antenna are you using? Is it impacted by weather?

What about outlier data / “freak out’s”? 

How good is your indoor weather ? (temperature etc in your lab)

Lots of variables. That’s nowhere near a complete list …

The issue is not - "don’t even try to test it". The issue is that testing takes more than just a little bit of time.


On Apr 27, 2014, at 9:44 AM, Tom Van Baak <tvb at LeapSecond.com> wrote:

> For a nice comparison of the M12+T, M12M, and ublox-6T, start with page 34, and especially note the ADEV plot on page 40:
> http://www.cnssys.com/files/tow-time2013.pdf
> The ublox-6T performs at least as well as the M12+T does. They are both in the 1 to 2 ns/day ballpark. The advantage is that the 6T is a production part and the M12+T and M12M are no longer made. So that's why commercial users have been forced away from the Motorola or iLotus parts. But amateurs still grab any M12 they can find because they are so good, and now dirt cheap on the surplus market.
> Note that Rick Hambly created the (Synergy) SSR-6T, which is a ublox-6T on a M12+T compatible PCB. Using a PIC it transparently translates between motorola and ublox binary so that the board is h/w and s/w compatible with any M12+T; a drop-in replacement. The plots you see in that PDF are the result of comparing M12+T and ublox-6T for this project.
> See also:
> http://www.gpstime.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf
> The bottom line is if you're looking for a low-budget but very high-performance GPS timing receiver, the M12+T is still a favorite among amateurs. If you're looking for something more modern, or a GPS timing receiver to use in quantity, or want an architecture that does or will accommodate Galileo and GLONASS, and are willing to pay the higher price, then check out the ublox-6T.
> /tvb
> ----- Original Message ----- 
> From: "Chris Albertson" <albertson.chris at gmail.com>
> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Sent: Saturday, April 26, 2014 10:36 PM
> Subject: Re: [time-nuts] New timing receivers?
>> How does the u-bloc's performance compare to the M12+T?    One of these is
>> on my list of things to buy someday.   I thought the M12+T had a 1-sigma
>> error in the single digit nanoseconds.    The u-bloc is newer it is even
>> better?
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