[time-nuts] Venus838LPx-T opinions?

Nick Sayer nsayer at kfu.com
Sat Jul 23 04:05:04 EDT 2016

The NMEA STI,00 message gives a sawtooth correction. I believe what Mark was saying was that there was no *binary* message that said so… maybe? I dunno. But the datasheet clearly talks about PPS quantization error compensation:

STI,00 – 1 PPS timing report

An output message, id 0x0, contains information of 1 PPS timing mode, 1 PPS survey length and 1PPS quantization error.

$PSTI,00,x,xx,xx *hh<CR><LF>

Example: $PSTI,00,1,1985,-12.4*1E<CR><LF>

Here there’s a table that I’ll try to interpolate because pasting it failed…

the 1 is the PPS timing mode. 0 = PVT, 1 = Survey mode, 2 = Static mode
1985 is the survey length
-12.4 is the PPS quantization error
1E is, of course, the checksum.

> On Jul 22, 2016, at 11:40 PM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
> Mark wrote:
>> Oh, and besides the lack of a binary message with satellite position/signal levels,  there is none that reports the sawtooth error.
> How in the world can they call it a "timing receiver" if it doesn't even support sawtooth correction??  Good grief.
> Also, I see they claim 6nS accuracy.  That is pretty much exactly 1/2 cycle of the main clock frequency, so +/- 6nS should be the expected theoretical best possible error envelope WRT the quantization error, *assuming the receiver's timing solution is always perfect.*  Are we supposed to believe they achieve that accuracy in practice, despite all of the well-known sources of error in GPS timing solutions??
> Best regards,
> Charles
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