Signal Status, Lock, Computations, Antenna for TomTom GO 300

[monkey_penny]

I want to get a better understanding of TomTom GO 300 signal strength, time to lock onto satellites, time to compute exact positions, and internal & external antennas.

1. I understand that the TomTom acquires a signal of at least one satellite, finds more satellites based on that digest information, and then computes your exact position based on computation of information from four satellites. The signal bars are gray in color while this done.

a. Assuming that four signal bars are gray at a steady level of at least ~25-28, how long should it take to compute an exact position?

b. Assuming that four signal bars are gray at a steady level of at least ~25-28, how, why would it take a varing amount of time (e.g., 1 minute one day, and up to 5 minutes another) to compute an exact position (when starting in the same place each day, while using the TomTom every day)?

c. If an external antenna were to increase the gray signal bars to a higher level, say ~35-38), does that decrease the time for the bars to turn blue (i.e., to get a lock to compute an exact position)?

d. Why would it take several minutes to compute an exact position while standing still in an open field?

2. Where in the TomTom 300 is the internal antenna located? Does the signal strength vary significantly if the TomTom is mounted upside down?

3. Why does the amount of availabe free RAM gradually decrease? For example, on my unit, it starts with about 6M free after I unplug the unit from my computer, and gradually decreased to about 4.6M after a couple of weeks of using it. Does reduced free RAM, at the ~4-6M levels, increase the time it takes to acquire four satellities and compute an exact position?

Thank you.

[lbendlin]

satellites ae not geostationary. They orbit every 12 hours (roughly).

So you always end up with different constellations, and that influences your lock time.

It's no good having five sats locked onto when they are all in one line...sats need to be as far apart from each other as possible.

external antennas help to use signals from sats that would otherwise be discarded as unreliable (below a certain SNR value)
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Lutz

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