Guidelines for Avoiding Terrain Obstructions
The HopNet transceivers operate in the 2.4 GHz frequency band. While this
band offers many advantages over the VHF band for data transmission, it is
also more prone to signal attenuation from obstructions such as terrain,
foliage, buildings and anything else in the transmission path.
Use the following guidelines to avoid terrain obstructions:
•
A line-of-sight transmission path between the base and the associated remote
sites provides for the most reliable transmission path.
•
A line-of-sight path can be achieved by mounting the station antenna on a tower
or elevated structure that raises it to a sufficient level to clear surrounding terrain
and other obstructions.
•
The importance of a clear transmission path relates closely to the distance to be
covered. If the system is to cover only a limited geographical area such as 1-3
miles, then some obstructions may be tolerated with minimal impact.
•
For longer-range systems, any substantial obstruction in the transmission path
could compromise the performance of the system.
RF Tools
Range Optimization.
On the RF Tools tab in the HopNet Configuration Wizard, the
Range Optimization function is used when the HopNet radios will be covering ranges of
more than one mile. The distance optimization parameter is needed to tell the radio
when to look for the acknowledgement from the receiving radio. This function will
automatically detect the best setting for this parameter and save it in the radio. The
value is only required in the remote radio and not the base. Different remotes at varying
distances from the base will have different values for this parameter. This function can
take several minutes to complete.
Receive and Bi-Directional Transmissions
. The Receive Only function displays the
percentage success rate for receiving transmissions from the base. This is an indication
of how well the remote HopNet “hears” the base. The Bi-Directional function provides a
round-trip success rate. That is, the base must successfully receive data from the
remote and the remote must successfully receive data from the base. In theory, this
percentage should be the square of the Receive Only percentage. If it is substantially
less, it is an indication that the base HopNet is having difficulty “hearing” the remote.
Good RF links will have the Receive Only percentage above 95% and the Bi-Directional
percentage above 90%. These functions operate with the Automatic Retransmit
Request (ARQ) disabled and as such provide an indication of link quality but do not
provide an indication of how often data will get through since in normal operation ARQ
is enabled and the radio automatically and transparently will resend data that was not
received on the first attempt.
Copyright © Murata Manufacturing Co., Ltd. All Rights Reserved. 2012
HN-210D/X, HN-214D/X Rev. 2.0 01/13/17
58 of 64
www.murata.com
