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MHX921 Operating Manual: Chapter 2 General
TDMA (time division multiple access) support, allowing
multi-slave access in point-to-point mode.
roaming ability, allowing repeaters and slaves to re-
synchronize with a new master if the synchronization pulse
from the original master is lost.
While the typical application for the MHX921 is to provide a short- to mid-
range wireless communications link between DTEs, it can be adapted to
almost any situation where an asynchronous serial interface is used and data
intercommunication is required.
2.1 Output Power Level
The Output Power Level determines at what power the MHX921 transmits.
The MHX921’s sensitive receiver can operate with very low power levels,
so it is recommended that the lowest power necessary is used; using
excessive power contributes to unnecessary “RF pollution”.
Ideally, you should test the communications performance between units
starting from a low power level and working upward until the RSSI is
sufficiently high and a reliable link is established. The conditions will vary
widely between applications, the output power settings can be calculated
based on following information.
•
Transmitter antenna gain
•
Cable loss
•
Equivalent Isotropically Radiated Power (EIRP) requirement by FCC
Regulations
Power Setting = 36 – Antenna Gain – Cable Loss
The power setting must be no more than the above calculation value.
Any
higher is a violation of FCC rules. See IMPORTANT warning below.
Table 1 Output Power
Power Setting
(dBm)
Approx. Output Power
(mW)
0 1
20 100
21 125
22 160
23
200
24
250
25
320
26
400
27
500
28
630
29
800
30
1000
