Cable & Wireless Optus

Report

DE21 RTC Modification Version 1.0

1. Introduction

1.1 Purpose

Due to the non-availability of the DE21 extension RTC shelf from Nokia it has been investigated and proven possible by Field Operations in South Australia to modify an existing Nokia RTC basic shelf (which are readily available) to act as an extension RTC shelf. The function of the extension shelf is to extend RF and DC connections to additional CFUAs (cavities & isolators) thus allowing greater than 4 TRXs to be connected to one transmit antenna. Using the modification described below an additional 2 CFUAs (4 TRXs) can be added to DE21 sites, giving a total of 8 TRXs in omni configuration.

The intelligence for the additional tuners resides in the basic rack, needing only an additional SMDA (Servo motor board) to be plugged in, in order to give control of an extra 4 tuners, this board can be obtained from the basic shelf under conversion.

The genuine Nokia Extension RTC provides 3 additional CFUAs (up to 6 TRXs), the modified basic rack however, will only provide 2 additional CFUAs (up to 4 TRXs) unless significant metalwork modification is carried out to allow insertion of the extra CFUA. SD&O SA (who initiated this conversion) envisage 2 additional CFUAs as sufficient given that this will allow up to 8 TRXs which should be adequate for most situations. Performance of the modified RTC shelf matches that of the basic shelf and as a complete system provides a total insertion loss of 4.6dB (proven during testing).

1.2 Scope

The scope of this document is to show how to successfully convert a DE21 RTC Basic shelf to an Extension shelf. For procedural information on expanding DE21 BTS beyond 4 TRXs (RMCE connections etc.), readers should refer to their standard Nokia documentation.

1.3 Definitions

BTSBase Transceiver StationDE21Nokia 2nd Generation BTS

TRXTransceiverRMCEReceive Multi Coupler

RTCRemote Tune CombinerCFUACombiner Filter Unit Assembly

2. Conversion of DE21 RTC Basic Shelf to Extension Shelf

2.1 Basic Shelf modifications

Within the Extension shelf only the shelf, filter equipment and some cabling are required, hence the following components can be removed:

COCA.

DECA.

AMCA.

TFUA.

SCAAs.

AMCA.

SMDA (relocate to the basic shelf).

Additionally the motherboard, DC connections from the front panel and ribbon cables can be removed. This will leave only the TX N type front panel connections to SMA right angles and the NRTC panel in place with N type connector to SMA right angle.

On the removed motherboard, 2 components will need to be removed for reuse, they are R1 & R2, positive temperature coefficient devices. These components will be required in the Extension RTC (detailed further on).

2.2 Internal Bus / Control Cabling

The major part of the job is to connect the DC, temperature compensation and control connections from the CFUAs to the internal bus 1/2 euro connector on the basic rack. To do this again as cheaply as possible a small extension board from the donor basic rack is used to allow connections to be made to 4 new 10 core ribbon cables that go to the CFUAs. This board resides behind the internal bus connection panel of the basic rack. Feed through holes on the board allows soldered connections to be made to the ribbon cables and the result is a satisfactory connection.

The diagram above shows how cores from the 4 ribbon cables are connected to the small PCB used from the donor shelf. The red trace on the ribbon marks core number 1 and corresponds to the triangle mark in the 10 way bump polarised socket to be pressed onto the ribbon cable. Stripped and tinned ribbon cable ends are fed carefully into feed through holes on the PCB. Cores 3 & 4 from all ribbons are commoned together and connected to the +V connections, which is at +4.8v.

Cores 5 & 6 are commoned together and connected to the Gnd connections. Cables can be stripped and twisted together before soldering and heat shrinking the joint.

Ribbon lengths are 450mm for tuners 5 & 6, and 600mm for tuners 7 & 8. Ribbon cable and 10 way connectors can be purchased from Force or Altronics stores for a few dollars. The recovered PTC semiconductor devices from the donor motherboard are soldered onto the board as indicated.

Parts required.

2.5m of 10 core ribbon cable.

4 of 10 way Bump polarised sockets to suit ribbon cable, (to plug into CFUAs).

Control Bus PCB showing the relative re-installation positions of positive temperature coefficient devices R1 & R2.

2.3 Internal Bus / Control Cable

The front bus cable connecting basic rack to extension rack needs to be made up also. This is a 1/2 Euro to 1/2 Euro lead providing the DC, temperature compensation, and control signals. Use four 1/4 euro connectors which are readily available to make up the leads using 0.4mm wire and correct wrapping tool. The design of this cable is such that it can be plugged in either way around and still be correct.

Upper connector toLower connectorUpper connector toLower connectorUpper connector toLower connector

A1A15B1B15C1C15

A2A14B2B14C2C14

A3A13B3B13C3C13

A4A12B4B12C4C12

A5A11B5B11C5C11

A6A10B6B10C6C10

A7A9B7B9C7C9

A9A7B9B7C9C7

A10A6B10B6C10C6

A11A5B11B5C11C5

A12A4B12B4C12C4

A13A3B13B3C13C3

A14A2B14B2C14C2

A15A1B15B1C15C1

2.4 RF Cabling

To reduce costs it was decided to take the Pf (forward power) and Pr (reverse power) connections directly from the CFUA connections to the front panel of the basic RTC to the SCAA connections (SMBs). The cost is then for 8 x SMA right angle, 8 x SMB right angle and some RG174 cable.

Make up 4 cables 580mm long for tuners 5 & 6, and 680mm long for tuners 7 & 8, SMB right angle one end and SMA right angle the other using RG174 cable. Heat shrink over the connector end and coax for neatness, see below for Rojone part numbers.

The existing cable from the NRTC connection (Old basic rack to extension rack internal cable ), N type to SMA right angle, needs to be made shorter to a length of 360mm and the right angle SMA connector changed to a straight SMA connector, Rojone part below. Keep the off cut cable and right angle connector as this will be used for the rear cavity connection.

The connection from the rear cavity TNC female to the existing SMA male jumper cable from the front CFUA T piece uses the off cut from the above NRTC cable mod and a Female-Female SMA barrel connector, part number below. Use the off cut and fit a TNC male connector onto it as per lengths in the diagram. This will make a neat connection to the rear cavity as the SMA female T piece is not required and will keep cable lengths correct.

If only one cavity is used in the extension then the T piece is removed and the new TNC to right angle connector plus the Female-Female SMA adaptor is used to make the connection to the front CFUA TNC connection.

The front connecting cable between the N type female sockets on the basic and extension shelves was obtained by modifying a DE34 TRX to AFEH cable, these cable sets are available from stock. Choose one end connector and peel off the crimp sleeve using large side cutters. Unscrew the cap from rear of the connector body and use a soldering iron to remove the centre core. Cut the Teflon coax to length as per diagram, solder the centre connection and crimp using a RG58 crimp sleeve (from any RG58 connector).

Alternatively 2 right angle N type connectors to RG223 coax could be used, parts purchased from Rojone, N type right angle to RG223 is part number R-161183.

Rojone Part Numbers

R-114186 - SMB right angle to RG174 crimp (8 reqd).

R-125172 SMA right angle to RG174 crimp (8 reqd).

R-125076 SMA straight to RG223 crimp (1 reqd).

R125705 SMA Female-Female adaptor.

R-143082 TNC male to RG58 crimp.

R-520-14-297A Crimp sleeve for above connector to suit teflon cable.

The pictures below highlight the modified RTC connections.

Left over blank panels can be used to cover the front of the shelf where cards have been removed. TX input numbering will need to be re-labelled as per the diagram to indicate the correct tuner number.

2.5 Installation / Configuration

Install unit below the basic RTC shelf and cable the Pf , Pr, RF and bus cables between the shelves. Install the additional SMDA card next the existing unit in the basic shelf.

The shelf behaves the same as the genuine extension RTC, no changes required. Configure the hardware database to reflect the number of TRXs installed and verify the TX cabling from the TXUA (or TXUB) is through to the specified tuner input on the RTC. All should function correctly and carrier levels at the antenna port should be the same for all TX signals.

3. Document Control

Authorisation

A.AuthorsDarren Phillips & Bruce Kerr

B.AuthorisedGeoff Hobby23/07/2003

C.ApprovedJohn Bolton23/07/2003

Amendment List

VersionDateSectionNature of AmendmentAmendment Author

Draft 1.018/07/03GeneralTechnical Content & DrawingsDarren Phillips

Draft 1.121/07/03GeneralFormatting & PicturesBruce Kerr

Ver 1.023/07/03GeneralFinal Formatting & ReleaseBruce Kerr

Cable & Wireless Optus

Report / 23 July 20031 of 1Optus

DE21 RTC Basic Shelf to Extension Shelf ConversionPage 1