User's Manual

www.malags.com

5 Shielded antennas

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Presently, Malå GeoScience manufactures 100, 250, 500, 800

MHz and 1 GHz shielded antennas. The 100, 250, 500 and

800 MHz antenna’s interface with the Shielded Electronics Unit

is described below (see also Fig. 5.1 to 5.4). The 1 GHz

antenna contains its own built-in transmitter and receiver

electronics and is described in Chapter 6.

A shielded type of antenna means that the energy is only

transmitted in one direction. It is also insensitive to radiation

from all directions except from the bottom part of the antenna

where the receiving antenna element is located. The shielded

antenna element comprise both transmitter and receiver

antenna elements in a single housing. These consist of a

modified bow-tie antenna construction with the receiver

element at the front end and the transmitter element at the

back of the housing.

The front of the antenna is equipped with a hook for attaching

a tow handle or strap. A fastening device at the back of the

housing accommodates the distance-measuring wheel This

wheel operates as a triggering device instructing the

RAMAC/GPR system to collect traces at operator pre-set

distant intervals (see Chapter 9). Detachable wear plates to

help insure long antenna life are also provided. See Figures

5.1 and 5.2.