Inside a Garmin 18 LVC GPS
Those of us who own a Garmin 18 LVC GPS, may have wondered what is inside the plastic body. Due to an unfortunate accident with an 18LVC ( that had been “run over” by the rolling roof of an observatory) - we can look inside without having to harm our own GPS, by viewing the following four images.
Because the GPS is classed as water-proof, please do not try and open the case yourself, otherwise it will allow moisture inside and decrease the life of the GPS.
To see more detail, click on the following images to see a larger image.
The following image shows the antenna (upper) side of the GPS. The actual tuned aerial is the part with A09 583 stamped on it, this is shaped to act as a circular polarised element for the GPS signals from space. Below that is a white ceramic block that allows a much smaller aerial, than if air was used as a dielectric, as explained in this home made patch antenna.
The following image shows the base of the GPS, where we can see the four (round) magnets embedded in the plastic base - that allow the GPS to "stick" to iron (like a car roof). We can also see the metal casing on the bottom of the (green) pcb. The electronics that do all the signal decoding, and thus derive position and time, are contained under this metal shield.
The following image is another view of the patch antenna looking down on the base.
NOTE: The above images are of a Garmin 18 LVC ( not an 18x model ).
Thanks to Vince for the photos.
A very useful lcomparison between the Garmin 18 and 18x - by Gerhard Dangl.
Kiwi Geoff (April 2009).