[ntp:questions] Sure board not seeing sattelites.

A C agcarver+ntp at acarver.net
Wed Feb 22 04:09:50 UTC 2012

On 2/21/2012 15:49, unruh wrote:
> On 2012-02-21, unruh<unruh at invalid.ca>  wrote:
>> I am having trouble with my Sure gps. I have the gps inside and have run
>> the antenna out to the edge of the roof ( the window looked out on a
>> bunch of trees, which seemed to block the gps a lot). The antenna sees
>> about 1.4 of the sky which should be lots to see enough sattelites to
>> get a time fix. However, I am finding that it will suddenly stop getting
>> a fix for long periods of time ( almost 15 hours now).
>> Here is an output from the unit right now.
>> $GPGGA,230334.993,,,,,0,0,,,M,,M,,*4E
>> $GPGSA,A,1,,,,,,,,,,,,,,,*1E
>> $GPGSV,3,1,11,32,86,163,,20,62,291,,31,60,077,,01,39,224,*77
>> $GPGSV,3,2,11,23,31,262,,14,19,072,,11,18,212,,30,16,136,*7D
>> $GPGSV,3,3,11,25,15,041,,17,04,294,,13,03,255,*41
>> $GPRMC,230334.993,V,,,,,0.00,228.53,210212,,,N*47
>> which seems to say that it is seeing some of the sattelites, but not
>> getting a fix at all. The blue light is not flashing.
>> I have no idea what is happening here.
>> Any suggestions?
>> The antenna is on the edge of the flat roof. There are two large cedar
>> trees to the east about 3m away partially blocking about 1/3 of the sky.
>> If you want to see it, go to 49 15' 59.68N  123 15 06.09W. The trees The
>> building extention to the west is about 2.5m high so does not block out
>> that much of the sky. There seems to me to be no reason why the system
>> should not be seeing enough of the sky to get enough sattelites for a
>> fix. Defective unit?
> And suddenly after about 18 hours of not working, it works again Here is
> a working report
> $GPGGA,234516.000,4915.9961,N,12315.1042,W,2,10,0.80,91.3,M,-16.9,M,0000,0006
> $GPGSA,A,3,23,20,32,31,30,04,01,13,25,16,,,1.37,0.80,1.12*09
> $GPGSV,4,1,13,20,75,248,47,32,66,148,46,23,47,275,52,31,46,056,51*7F
> $GPGSV,4,2,13,30,31,123,34,01,22,212,46,13,17,266,44,16,14,144,28*76
> $GPGSV,4,3,13,04,11,325,46,25,08,026,40,14,04,081,35,11,04,204,18*74
> $GPGSV,4,4,13,33,,,*7B
> $GPRMC,234516.000,A,4915.9961,N,12315.1042,W,0.00,228.53,210212,,,D*7F

You might be suffering from multipath.  I had a similar problem when I 
first moved into this place.  I had the antenna on a post but, without 
thinking, I put it near a satellite dish left behind by the previous 
tenants.  Before moving here it was sitting in a window and doing well. 
  After moving here it was doing poorly, barely ever receiving signals 
even though I had an even larger view of the sky.  Signal levels, when 
they could be measured, were in the low 20-30 db-Hz.  On a whim I moved 
the antenna about 3 meters further away from the original location and 
signal levels jumped to 40-50 db-Hz.

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