Installation________________________________________________ Boomer-III User Manual & Integrator’s Guide
Copyright Wavenet Technology © October 2003
40
BM310012WT04
Cabling demands the same consideration as an internal antenna
application. In a typical laptop application, the antenna must be placed
as far as possible from a display to avoid deflection. This usually
causes a deep null in radiation patterns.
External, remote antenna
For remote antenna application use the same design approach as
internal designs, including the RF cable routing of the external
connector. You can choose an off-the-shelf mobile antenna of omni
directional ½ wave length.
A double braid coaxial cable such as RG223 from the device to the
antenna is recommended if the cable length is more than a metre. The
difference in cable loss between low cost RG58 and the more
expensive RG223 is approximately 4.5dB per 30 metres. If the cable
must be routed through noisy EMI/RFI environments, a double braid
cable such as RG223 can reduce radiation and pick-up by 30 to 40dB.
Fixed Devices
Fixed data device applications use the same design recommendations
as a portable device with a remote antenna.
As for the RF connector of an external antenna, whether it is a plug-in
type or a remote type, the most economical and practical choice is a
TNC threaded connector. TNC has a good frequency response to
7GHz, and leakage is low. A mini UHF threaded connector provides
adequate performance and is an economical choice. If the size of the
TNC and mini UHF connectors becomes critical, consider an SMA
threaded connector or an SMB snap fit connector. (The SMB connector
does not accept an RG58 or RG223 cable).
Selecting an Antenna
The requirements for the antenna used with the Boomer-III OEM
Modem are:
Antenna Gain:
5dBi (isotropic) maximum average gain if
modular FCC approvals are to be used
without separate equipment approval for
the host/terminal.
Impedance: 50
Ω
Centre Frequency:
833MHz ± 5MHz (for 800MHz modem)
Frequencies of operation:
806 to 825MHz (for 800MHz transmit)
851 to 870MHz (for 800MHz receive)
Acceptable return loss:
VSWR < 1.5 or RL < -14dB (recommended)
VSWR < 2.0 or RL < -10dB (minimum)
The power output of the Boomer-III OEM Modem is nominally 2W at
the antenna port. The antenna gain or loss will affect the radiated value.
