105 Radio/Serial Telemetry Module
User Manual
Page
66
©
January 2004
Signal
This option provides for testing the radio path between two 105-U units for a suitable fade
margin. Although a pair of units may communicate successfully, radio communication may
be affected by a range of influences, including atmospheric conditions, changing landscape,
degradation of antennas or co-axial cable, low battery voltage etc. Fade margin is an
indication of how far a radio path can deteriorate before communication becomes unreliable.
When using the Signal feature, a meter is displayed with a mark indicating the current
received radio signal level. To check the radio path between two units, select the signal option
at the local unit. The remote unit may then be set up for tone reversals (refer 1 above) and the
signal level read from the meter.
A simpler method when remote units are not easily accessible is to cause a transmission from
the local unit to the remote unit (by setting a digital input which maps to the remote unit, for
example). The meter will latch the received signal from the remote unit for half a second,
allowing the received level to be read.
Under normal radio conditions, a reading of 0 indicates a very marginal communication path.
For reliable communications, the signal reading should be 3 or above.
>k
Minimum signal level for reliable comms
Signal
0123456789----
#
In areas experiencing radio interference or high background noise, reliable communications
may not be achievable even with this signal level. To determine if interference is occurring
the signal option may be selected without any other 105 units active. In a normal radio
environment, no reading should be displayed. If a reading is displayed, then
the received
signal strength from the remote should be at least three counts higher than the
background noise
for reliable communication.
>k
Displayed signal level of
Signal
background noise/interference
0123456789----
#
>k
Minimum signal level for reliable comms
Signal
0123456789----
#
When using directional antennas (i.e. YAGI antennas) this feature may be used to peak the
received signal level. Set-up the remote unit to transmit tone reversals as described above,
and observe the signal indication while adjusting the orientation of the antenna. A peak in
signal level indicates optimum orientation of the antenna.