[time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

Bob kb8tq kb8tq at n1k.org
Mon Jan 22 12:43:39 EST 2018


It is doubtful that the pc board has an RS-232 to TTL converter onboard. The module it’s self
“talks” TTL levels rather than RS-232 levels. RS-232 to TTL adapters are dirt cheap and easy
to find on eBay. Make sure you get one that has control lines along with the basic RX and TX
functions. (You need to buffer the PPS signal). They also allow you to put in a “pulse stretcher”
on the PPS if the default is to short for your computer.

There is no value in a “timing” GPS vs a “normal” GPS for NTP. As long as you have a PPS output,
you are good to go. As noted elsewhere, something like the more modern M8 series is just
as cheap and will do a better job. Simply get any of the modules and an adapter. Hook them up
and move on. Total cost should come in < $30 delivered. 

There are tons and tons of details on how do do all this in the archives. 


> On Jan 22, 2018, at 10:38 AM, Paride Legovini via time-nuts <time-nuts at febo.com> wrote:
> Dear fellow nuts,
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
> As far as I can tell there are a few common options. One is the Trimble
> Resolution T (or SMT), that should be good and proven. The major
> annoyance is converting the 3.3V TTL serial logic-level to RS232, but
> should be doable with a MAX3232 and a few capacitors.
> Another option is this UBLOX LEA-5T:
> https://www.ebay.it/itm/291769145465
> The seller advertises an RS232 output pin, but I'm not sure it's
> actually available, and I'd need at least lines, one for the NMEA
> strings and one for the 1PPS signal. So, even if a RS232 TX pin is
> actually there, it is probably not enough to build a good reference
> clock, and I'd still need to convert some TTL levels to RS232...
> Does anybody have experience with this receiver?
> How does it compare to the Resolution T/SMT?
> Another option is the Trimble Thunderbolt. This seems to do exactly what
> I need, but it costs at least ten times more than the other modules.
> Beside coming with a ready to use RS232 port and a nice case, does it
> have other advantages?
> Am I overlooking something or missing interesting options?
> Cheers,
> Paride IZ3SUS
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