User's Manual

2 MHX-920 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 MHX920 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 MHX920 transmits.
The MHX920’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
• Effective radiated power (ERP) 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