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(ADMIN ONLY)Bulletin Number: GSM_G_BSS_118 

EMEA Swindon CNRC # +44 (0) 1793-565444 Motorola General Business Information

ASPAC CNRC# +86-10-8841-7733 ECCN#

WCN#gsmgbss2508041358

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Bulletin Number: GSM_G_BSS_118POPI Status: Motorola General Business Information

To: All GSM Local Offices and Customers Publication Date: 27 August 2004

From: EMEA Customer Support Centre Expiration Date: 27 February 2005

Title: Transmit VSWR Alarms indicated by Horizon II macro  

Overview: This bulletin provides information on the detection and resolution of Tx VSWRissues using alarm DRI 78 and DRI 73 on Horizon II macro BTS

Affected Hardware: 900 Horizon II macro BTS

1800 Horizon II macro BTS

Affected Software: N/A

Applicable PRs/MRs/SRs: N/A

Applicable Bulletins: N/A

Affected Manuals/Reference Manuals: N/A 

Problem Description

Horizon II macro incorporates a transmit VSWR detector. When an antenna system fault is detected,an alarm DRI 78 is signaled. A DRI 73 alarm can also be a symptom of a more severe VSWR than

DRI 78.

This bulletin explains the impact of this alarm, its cause, and the action required to resolve it.

Technical Description

This new feature, which has been introduced in the Horizon II BTS, provides monitoring of transmitantenna VSWR. The hardware functionality that measures returned Tx power has been integratedinto the cabinet duplexer. If a poor VSWR condition is detected, the operator will be alerted with aDRI 78 alarm “Tx VSWR Antenna Fault”. This indicates that there is a high level of transmit powerbeing reflected from the antenna system and indicates a possible fault condition. In extreme cases ofpoor VSWR, a DRI 73 alarm “Power Amplifier Error” might occur. In these cases, a large amount ofpower is being reflected back to the CTU2.

Based on recent field investigation of DRI 78 and 73 alarms, the primary root cause of these alarmshas been the case of a bad feeder cable, a bad lightning arrestor, and/or poor installation practices.For example, a loose cable connection between the antenna and the feeder cable that is exposed

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(ADMIN ONLY)Bulletin Number: GSM_G_BSS_118 

EMEA Swindon CNRC # +44 (0) 1793-565444 Motorola General Business Information

ASPAC CNRC# +86-10-8841-7733 ECCN#

WCN#gsmgbss2508041358

Final Document  Date Printed: 04/10/2002 Page: 2 of 2

 

outside and is not properly sealed may accumulate moisture/water resulting in a degradation ofconnection over time.

Action Required

Based on field investigations, the first action should be to review the event logs at the OMC andschedule a site visit to correct the fault on the antenna system.

At the site, measure VSWR at BTS output port (Duplexer Output) and verify it’s < 2.61:1 (Return Loss> 7 dB). If VSWR is poor, troubleshoot to identify the faulty component in the Tx path and replace or

repair the components as necessary.

If a DRI 73 occurs but no reverse power is present, then inspect the DUP input, CTU2 to DUP SMAcable, or the CTU2 output connector itself.

Preferred Method of Resolution

A White Paper has been written to provide further details on the VSWR alarms functionality andmethods of troubleshooting the BTS to find the exact fault. This document can be found at thefollowing http://compass.mot.com/go/148942400. 

All Motorola product names are trademarks or registered trademarks of Motorola, Inc.

End of Document