[ntp:questions] NTP NMEA driver

unruh unruh at invalid.ca
Thu Feb 14 21:56:02 UTC 2013


On 2013-02-14, Mischanko, Edward T <Edward.Mischanko at arcelormittal.com> wrote:
> And what exactly is wrong with the Garmin 18x?  I have found my 18x to be
>  much more stable than the Sure Electronics one.

The Garmin 18x had a bug in its firmware so that itsometimes  put out the time
over a second after the turn of the second. 
 Time -------->
Second.number.......1............2..........3
PPS.time............x............x..........x
Garmin.output.........0............1..........2

They have since put out a fix to the firmware in the recievers which
fixes this. so that we now get (as we should) 

Second.number.......1............2..........3
PPS.time............x............x..........x
Garmin.output..............1..........2..........3

(The periods are there to ensure that the formatting does not get
screwed up)

You claim it is more stable. What is the evidence of this that you see?
(The Gamin has a claimed accuracy of about 500ns)

I had two Gamin 18 receivers. Unfortunately both died after about 3
years of use. 

I also have two Sure receivers, but on one the antenna was defective.
They never sent me a replacement although they said they would. 




>> 
>> You are always at the mercy of the receiver.
>> And it is not the fix time. ZDA puts out only to the nearest 10 ms. the
>> others to the nearest second or 10ths of a second.  Fix
>> times are in the nanosecond realm. They put out times which are the time
>> label of the latest second (or they should if they are not incompetently
>> designed as the Garmin 18x was.)
>> 
>> 
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