Gps Reception

[+woodworkerjason]

I ordered a Garmin etrex Vista on monday and have been looking through this forum about it losing signal under trees. The GPS I'm replacing is a Garmin GPS12 because of the maps and extra features. I've never lost a signal with my GPS12 even in deep valleys and under trees. I even get a signal when I'm inside the house. Is the Vista antenna inferior to the GPS12?

 

Thanks for any info anyone has.

 

-Jason

[Prof. Y. Lupardi]

There is a lot of hoolabaloo about the gimmick 'antenna' at the moment.

There is not that much difference between the types. Fundamentally it is a question of: how much energy is recieved by the antenna and how good does the antenna swing with the signal: gain.

Materials become better and gain goes up but the net effect is not much better because the antenna's are made smaller and smaller recieving less and less energy and more and more noise.

Stop thinking in terms of analog reception. F.I.

You know the terrible effect when listening to far away shortwave radiotransmitters and getting the signal by two or more ways. Reception comes and goes.

Not so in the digital world.

Take this situation: I have a digital reciever tuned to a transmitter and I am getting 1Mb/s across.

Then I put a second transmitter on the same frequency also doing a bitstream of 1 Mb/s. I will recieve 2Mb/s because the digital processing is able to unravel this mix I am recieving.

Another one:

I recieve a WiFi station by direct line of sight but also by a reflection from a big building. Is that bad? No, just the opposite: the extra available reflected time-delayed signal bits can be taken out digitally and added to the direct recieved bits making a sturdier bitstream.

The same kind of things are going on in a GPS.

So when someone observes that antenna A is better the B then what he is seeing is a difference between the units in the way the digital processing is done.

A firmware update can change the behaviour of your GPS in such a way that you think you suddenly have a better antenna!.

[+PDOP's]

Is the Vista antenna inferior to the GPS12?

 

Thanks for any info anyone has.

 

-Jason

The GPS 12 and eEtrex models both use a patch type of antenna. A quote from this webpage about GPS antenna specs.

 

"Note also that the eTrex models are more compact units than the others listed. As a result, they have slightly less antenna gain (on the order of perhaps 2db less) than the physically larger models and thus will have slightly less sensitivity which may be important under forest canopy"