[ntp:questions] Sure gps looses all sattelite fixes

unruh unruh at invalid.ca
Mon Feb 27 16:49:39 UTC 2012

On 2012-02-27, Hal Murray <hal-usenet at ip-64-139-1-69.sjc.megapath.net> wrote:
> In article <GH92r.13655$1I2.2503 at newsfe08.iad>,
>  unruh <unruh at invalid.ca> writes:
>>Agreed. I have now managed to get the GPGSV from a Garmin 18 located
>>about 5 m away on that same rooftop, and this morning I got a dropout
>>from the Sure again for about 5 min. while I was also recording the
>>messages from the Garmin. The garmin shows that during this time, the
>>weakest sattelites (35-40dB S/N) did show more dropouts, but for brief
>>times ( a few to about 10 sec) but the stronger (>40dB) showed no change
>>in their S/N during those times. (When working, The Gamin's minimum useable S/M seems
>>to be about 35dB, while the Sure goes down to below 20dB and still
>>tracking Of course when not working the Sure sees nothing)). 
>>The Sure again completely died over a time span of 3 sec, with all signals (including the 50dB
>>prior level signals) completely dropping out. It is still dropped out 6
>>hours later. 
> I have a Sure that dropped out for several days.  The number of satellites
> it was tracking faded to 0 and then stayed there for several days.
> A while ago, it dropped out for several hours.
> Several other units had similar troubles but mostly not as bad.  They are
> all located inside my house so I don't expect great operation.  I was
> surprised that it stayed off-the-air for so long.  A similar unit six
> feet away worked most of the time.
> What's a reasonable SNR as reported by GPGSV?

Ssure tracks with a S/N of between about 18 and 54. (higher is stonger)
The Garmin trackes with S/N between about 35 and 54.

What happens here is that the sattelites will be strong (S/N of 45-54)
then suddenly over the time frame of seconds, all loose tracking ( but
the gps still sees the sattelites and still reports their location in
the sky), and when they come back again they are at the 45-54 level. 
I have now seen one such dropout from the Garmin 18 that is located
about 5 m away from the sure antenna. (The sure at that time was offline
for about 15 hrs).

There seems to be some problem, wither with the antenna or with the
board. This kind of dropout behaviour makes the Sure much less useful
for timing purposes. 

 have written to Sure, but have had no response.


More information about the questions mailing list