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MHX-920 Operating Manual:Glossary

 

5

 

Figure 1  Gain Calculation 

The power level has been set to 30dBm (1W) on the transmitter, and the 
receiver sensitivity for the MHX920 is -108dBm.   

System gain would be calculated to be: 

30 - 2 + 6 + 3 - 2 + 108 = 143 dB. 

 

Figure 2 System Deploying 

When deploying your system, care must be taken to ensure the 

path loss 

(reduction of signal strength from transmitter to receiver in dB)

 

between 

equipment does not exceed the system gain (140 dB in the above example).  
It is recommended to design for a 

gain margin 

of at least 20 dB to ensure 

reliable communication.  Gain margin is the difference between system gain 
and path loss.  Referring to the same example, suppose the path loss is 100 
dB, the gain margin would be 40 dB, which is more than adequate for 
reliable communication. 

Path loss is a very complicated calculation which mainly depends on the 
terrain profile, and the height of the antennas off the ground.  

The following table provides path loss numbers for varying antenna heights 
and antenna separation:  These numbers are real averages taken from rural 
environments.  They do not apply to urban, non-line-of-sight environments. 

Table 2 Path Loss 

Distance 

(km) 

Base Height 

(m) 

Mobile Height 

(m) 

Path Loss 

(dB) 

5 15  2.5 116.5 

5 30  2.5 110.9 

8 15  2.5 124.1 

8 15  5 117.7 

8 15  10  105 

16 15  2.5 135.3 

16 15 

5  128.9 

16 15  10 116.2 

16 30  10 109.6 

16 30 

5  122.4 

16 30  2.5 128.8 

 

Base Height (m)

Mobile

Height

(m)

Distance (km)

Содержание MHX-920

Страница 1: ...MHX920 900 MHz Spread Spectrum OEM Transceiver Revision 0 10 January 9 2006 17 2135 32nd Ave N E Calgary Alberta T3K 4Z4 Phone 403 248 0028 Fax 403 248 2762 www microhardcorp com Model MHX920A Microh...

Страница 2: ...IONAL WARRANTY Indemnification The Purchaser shall indemnify Microhard Systems Inc and its respective directors officers employees successors and assigns including any subsidiaries related corporation...

Страница 3: ...d antennas Antennas not listed in the tables must be tested to comply with FCC Section 15 203 unique antenna connectors and Section 15 247 emissions WARNING MAXIMUM EIRP FCC Regulations allow up to 36...

Страница 4: ...ights ii MHX920 Regulatory Requirements iii CONTENTS IV 2 GENERAL 1 2 0 PRODUCT OVERVIEW 1 2 1 OUTPUT POWER LEVEL 2 3 INSTALLATION 4 3 0 OVERVIEW 4 3 1 ESTIMATING THE GAIN MARGIN 4 3 2 ANTENNAS AND CA...

Страница 5: ...exempt band of the radio spectrum1 this means that it can be used without access fees such as those incurred by cellular airtime a serial I O data port with handshaking and hardware flow control allo...

Страница 6: ...ry 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 be...

Страница 7: ...MHX 920 Operating Manual Chapter2 General 3...

Страница 8: ...ween a transmitter receiver pair The number can be calculated based on knowledge of the equipment being deployed The following four factors make up a system gain calculation 1 Transmitter power user s...

Страница 9: ...een system gain and path loss Referring to the same example suppose the path loss is 100 dB the gain margin would be 40 dB which is more than adequate for reliable communication Path loss is a very co...

Страница 10: ...2 Antennas and Cabling This section describes the recommended procedure for installing cabling and antennas for use with the MHX920 module 3 2 1 Internal Cabling The most common method for installing...

Страница 11: ...and any person when the device is in operation Surge Arrestors The most effective protection against lightning is to install two lightning surge arrestors one at the antenna the other one at the inte...

Страница 12: ...t If the equipment is in a fixed location and is to communicate with only one other unit also in a fixed location then a Yagi antenna is suitable Choose a Yagi with enough gain to ensure adequate gain...

Страница 13: ...he maximum power setting of 30dBm Example 2 What is the maximum power the MHX920 can be set to comply with FCC and IC given the following equipment given a Yagi Ant Gain 12dBd and cable and connector...

Страница 14: ...Directional Antenna Bluewave RPTNC Pigtail MHS031501 9dBd 900MHz Yagi Directional Antenna Antenex RPTNC Pigtail MHS031441 10dBd 900 MHz Yagi Directional Antenna Bluewave RPTNC Pigtail MHS031451 11dBd...

Страница 15: ...MHX 920 Operating Manual Glossary 11...

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