BendixKing SKYMAP IIIC - Manual (Page 27)

BASIC OPERATION
Antenna Considerations (Skymap IIIC only)
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The Skymap IIIC is supplied with a portable antenna that is convenient for use in
circumstances where the unit is removed from the aircraft regularly. Your Bendix/King
dealer can advise you on other antenna options to suit different applications or improve
performance.
When positioning the portable antenna, always ensure that the domed (the opposite
side to that which carries the CE marking) face of the antenna is facing straight up
to the sky and can “see” a large area of the sky, preferably right down to the
horizon. In order to provide a 3-dimensional fix, Skymap IIIC needs to receive signals
simultaneously from at least four satellites.
The radio signals from the GPS Navstar satellites are transmitted in an extremely high
frequency band (1.5GHz). They can be regarded as having approximately the same
penetration capabilities as light. This means that they are able to penetrate only
transparent or very thin materials and will be blocked by almost any material that blocks
light.
At least four and at times up to twelve GPS satellites should be in view from any place in
the world at any time. These can, however, be absolutely anywhere in the sky and so, to
ensure uninterrupted navigation it is essential that the antenna has direct line-of-sight
contact with as much sky as possible.
If the position in which you wish to locate your Skymap IIIC is shielded from the sky and
the standard antenna cable is not long enough for an acceptable installation bearing the
above guidelines in mind, you may choose one of several options for remote antenna
sitting. The simplest is to use the Bendix/King remote antenna extension cable. This
allows the portable antenna to be extended by a further 6ft (2 metres) thereby allowing
mounting up to 12ft (4 meters) away from the main unit. The antenna may be held in
place there by using the rubber suction cup supplied (which should be slotted into the key
hole in the antenna bracket) or fixed permanently in position by using the countersunk
screw mounting holes in the antenna bracket. The rubber suction cup is ideal for
temporary use in vehicles and light aircraft. The portable antenna is only splash proof and
not fully waterproof. Never mount this antenna permanently outside.
For permanent external antenna mounting an external magnetic mount antenna is
available for ground vehicles and an external low profile "tear drop" style antenna for
aircraft. For more information about these accessories please contact your Bendix/King
dealer.
Rev 9 Jul 2006 1-18 Skymap/Tracker IIIC Pilot's Guide