Slow geting fix on startup

PAQMAN · Regular Visitor Joined: May 18, 2004 Posts: 62

My BR305 used to get its first fix after about 25 secs, its now taking up to 3 mins, is this the beginning of a failure?

Dave · Posted: Sat Jul 24, 2004 11:39 am Post subject:

No, a cold fix usually takes 30 seconds minimum. Most average fixes will take around 1 min if the receiver has been powered off for several hours to a day or two. If you've been receiving fixes at 25 seconds or less, then you probably have had it switched off for less than an hour.

If it's taking 3 mins now to receive a fix, then it means it's having to re-download the data several times because it doesn't have a good view of the sky. This could be due to tree's, too close to a building, athermic windscreen, or you have some localised interference either in the car or outside the car.

PAQMAN · Regular Visitor Joined: May 18, 2004 Posts: 62

Dave Thanx for the reply, I dont disbelieve what you say, but it was always up and running in the morning before I was off my drive, now I can drive 2-3 miles before it starts recieving. Not changed anything, parked in same place, still in same place by windscreen etc etc. Cant understand it.

Dave · Posted: Thu Jul 29, 2004 11:27 am Post subject:

Providing the GPS has the almanac which takes 12.5 mins to download and no ephemeris table, e.g. completely cold fix, then the maximum time it will take is 30 seconds. Depending on how much data is left in the ephemeris table that is frequent, you may find you get quicker fixes, but if you've left the GPS overnight, then you're really going to be looking at 30 seconds +, and in most cases around 1-2 mins.

Hunnymonster · Posted: Wed Aug 04, 2004 8:32 pm Post subject:

As you move and it loses sight of the satellite it's downloading the ephemeris from, it'll start the download again from another satellite so the fact that you're moving will also slow the time to first fix.....

With the CF receiver I always switch it (and the iPaq) on before I get in the car and put the laptop bag in the back etc. and it's usually got a fix before I start the engine and move off.

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