Mantracourt Electronics Limited
T24 Technical Manual
83
Example 3
In practice the radios would be fitted inside enclosures and the antenna may be either inside the enclosure or
mounted some distance from the radio and connected to it by an extended feeder. A practical example of this
type is illustrated at Figure 2 below.
80m
G
T
=
4.5dB
G
R
=
6.0dB
Path loss = 70.46dB
Figure 2
G
T
= Gain of transmit antenna
G
R
= Gain of receive antenna
0dB
Tx
Rx
Feeder
loss
1.5dB
Enclosure Loss =
6dB
Sum of the gains = G
T
+G
R
or: 4.5 + 6.0 = 10.5
Sum of the losses = Feeder Loss + Path Loss + Enclosure Loss
or: 1.5 + 70.46 + 6.0 = 77.96
Signal strength at the receiver input is: 10.5 – 77.96 = -67.46dBm
Refer to Table 1 below that relates receiver input power to RSSI, an input level of -67.46dBm will give an RSSI of
around -74.
In this example the gain of the receive antenna and the receiver enclosure loss are identical and therefore cancel
out, this is what happens in the T24-HS. In the case of the T24-BS however, peak gain of the PCB antenna is 6dB
and the enclosure loss is between 3 and 5dB depending on composition of the ABS.
