Antennas; Uhf Antennas; Hf Antennas - ASCOM T942C System Installation

System Installation
Ascom Paging System
5

Antennas

Several types of antennas are used in the Ascom Paging System, such as ground-plane,
dipole and helix antennas but the choice of type should be made to suit the actual site. In
some cases other types of antennas may be required due to the terrain or climatic
conditions. Note that dipoles must be ordered for the correct frequency.
In general, Ascom Paging System antennas can be grounded if necessary, but large
potential differences between different ground points can cause problems. Therefore,
antenna grounding should be avoided if possible.
2 m
Figure 5. Antenna reliability measures.
5.1

UHF Antennas

UHF transmitters in the Ascom Paging System use a CXL-70, a broad band half wave
coaxial antenna for 406-470 MHz. The antenna is dc-short-circuited, and has an "N" type
connector.
CXL-70 is mounted at the top of an antenna mast or with a supporting boom. The boom
should be at least 0.5 m.
CXL-70 is designed to be insulated from the mast but is delivered with a nut and washer
that are screwed onto the antenna connector if the antenna ground (=coax shield) is to be
dc-connected to the mast.
Note: The nut and washer are normally not used.
In a two-way UHF system, a common base antenna with duplex filters can simplify the
antenna installation of receiver/transmitter pairs.
5.2

HF Antennas

HF installations can use the following types of antennas:
• GP-25L is a 25-175 MHz ground-plane antenna for mounting on a mast. The antenna
is frequency adjusted by cutting the fibre-glass elements to the correct length
according to the diagram that is delivered with the antenna. The antenna has a UHF
type connector.
10 October 2013 / Ver. D
GP 4103 HF
0,5 m
CXL-2
VHF
1,25 m
0,5 m
CXL-70
UHF
0,9 m
25% of
mast height
Wall brackets FM-103
Mast pipes Ø 50 mm x 3 m (2 ea)
TD 90227GB
8