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MHX921 Operating Manual: Chapter2 General

 

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2. General 

 

2.0 Product Overview 

The MHX921 is a high-performance embedded wireless data transceiver.  
Operating in the 902 - 928 MHz ISM band, this a spread-spectrum module 
is capable of providing reliable wireless data transfer between almost any 
type of equipment.  The small-size and superior RF performance of this 
module make it ideal for many applications.  
 
While a pair of MHX921 modules can link two terminal devices (“point-to-
point” operation); multiple modules can be used together to create a 
network of various topologies, including “point-to-multipoint” and 
“repeater” operation. Multiple independent networks can operate 
concurrently, so it is possible for unrelated communications to take place in 
the same or a nearby area without sacrificing privacy or reliability. 
 

1.1  Features

 

Key features of the MHX921 include: 

  transmission within a public, license-exempt band of the radio 

spectrum

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 – 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, allowing the MHX921 to interface directly to any 
equipment with an asynchronous serial interface. 

 

ease of installation and use – the MHX921 module uses a 
subset of standard AT style commands, very similar to those 
used by traditional telephone line modems. 

  all units in a system are physically identical, and can be 

configured as a master, repeater or slave using the AT 
command set. No hardware modifications are required 

  128 sets of user-selectable pseudo-random hopping patterns, 

intelligently designed to offer the possibility of separately 
operating multiple networks while providing security, 
reliability and high tolerance to interference. 

  encryption key with 65536 user-selectable values to maximize 

security and privacy of communications. 

 

32-bit of CRC error detection and auto re-transmit to provide 
accuracy and reliability of data. 

                                                           

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 902-928 MHz, which is license-free within North America; may need to be factory-

configured differently for some countries.

 

Содержание MHX921

Страница 1: ...ual MHX921 900 MHz Spread Spectrum OEM Transceiver Revision 0 30 April 7 2006 17 2135 32nd Ave N E Calgary Alberta T3K 4Z4 Phone 403 248 0028 Fax 403 248 2762 www microhardcorp com Model MHX921 Microhard Systems Inc ...

Страница 2: ...TIONAL WARRANTY Indemnification The Purchaser shall indemnify Microhard Systems Inc and its respective directors officers employees successors and assigns including any subsidiaries related corporations or affiliates shall be released and discharged from any and all manner of action causes of action liability losses damages suits dues sums of money expenses including legal fees general damages spe...

Страница 3: ...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 dBm equivalent isotropically radiated power EIRP Therefore the sum of the transmitted power in dBm the cabling loss and the antenna gain cannot exceed 36 dBm WARNING EQUIPMENT LABELING The FCC and IC n...

Страница 4: ...Rights ii MHX921 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 CABLING 6 3 2 1 Internal Cabling 6 3 2 2 Installing External Cables Antennas and Lightning Arrestors 7 ...

Страница 5: ...ctrum1 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 allowing the MHX921 to interface directly to any equipment with an asynchronous serial interface ease of installation and use the MHX921 module uses a subset of standard AT style commands very similar to those used by traditional tel...

Страница 6: ...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 set...

Страница 7: ...MHX921 Operating Manual Chapter2 General 3 ...

Страница 8: ...tween 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 selectable 2 Transmitter gain transmitting antenna gain minus cabling loss between the transmitting antenna and the MHX921 module 3 Receiver gain Receiving antenna gain minus cabling loss between the ...

Страница 9: ...ween 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 ...

Страница 10: ... procedure for installing cabling and antennas for use with the MHX921 module 3 2 1 Internal Cabling The most common method for installing the module is to run a cable from the module s MCX connector to a reverse TNC bulkhead connector on the chassis of the equipment as shown in Figure 3 This cable can be purchased from Microhard Systems Figure 3 Suggested Internal Cabling Cable losses are negligi...

Страница 11: ...stors The most effective protection against lightning is to install two lightning surge arrestors one at the antenna the other one at the interface with the equipment The surge arrestor grounding system should be fully interconnected with the transmission tower and power grounding systems to form a single fully integrated ground circuit Typically both ports on surge arrestors are N female External...

Страница 12: ...quipment 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 margin When deploying the Yagi point the antenna towards the intended target ensuring the antenna elements are perpendicular to the ground for vertical polarization In applications where there...

Страница 13: ...em to the maximum power setting of 30dBm Example 2 What is the maximum power the MHX921 can be set to comply with FCC and IC given the following equipment given a Yagi Ant Gain 12dBd and cable and connector loss of 4 5 dB Max EIRP 36dBm Max TX power EIRP Ant Gain dBi Cable Connector loss dB Ant Gain dBi Ant Gain dBd 2 15 dB Yagi Gain dBi 12 2 15 14 15dBi Max TX power 36dBm 14 15dB 4 5dB 26 35dBm W...

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 900 MHz Yagi Directional Antenna Bluewave RPTNC Pigtail MHS031401 12dBd 900MHz Yagi Directional Antenna Antenex RPTNC Pigtail MHS031411 12dBd 900MHz Yagi Directional Antenna Bluewave RPTNC Pigtail Om...

Страница 15: ...MHX921 Operating Manual Glossary 11 ...

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