Tait TEL0004 User Manual 8

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Document ID	79262
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Document Description	8
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Permanent Confidential	No
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Document Type	User Manual
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Filesize	18.68kB (233517 bits)
Date Submitted	2000-01-04 00:00:00
Date Available	1998-09-25 00:00:00
Creation Date	2001-05-03 11:13:24
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Document Title	8

m: CASTEL0004
2.983 (ans)
T830 Series II
Base Station Equipment
Service Manual
Preliminary Issue
August 1997
(Not For Resale)
Copyright TEL August 1997
About This Manual
Scope This manual contains preliminary servicmg information on T830
Series II 25W, 50W and 100W base stations which comprise the
following equipment:
25W base station T835 receiver
T836 25W transmitter
50W base station T835 receiver
T837 exciter
T838 50W power amplifier
100W base station T835 receiver
T837 exciter
T839 100W power amplifier
Contents Part A contains information on the following procedures:
changing the operating frequency
retuning the module after changing frequency
configuring the audio processor
T838/839 user information
Parts B to G contain the following PCB information:
parts lists
grid reference indexes
PCB layout diagrams
test points & options diagrams
circuit diagrams
Part H contains the following information on the T800~2270000
rack frame:
° general information
- circuitoperation
- parts lists
0 PCBlayoutdiagrams
Technical Information
Any enquiries regarding this manual or the equipment it describes should be addressed
in the first instance to your nearest approved Tait Dealer or Service Centre. Further
technical assistance and copies of this manual may be obtained from the Customer Sup-
port Group, Radio infrastructure Division, Tait Electronics Ltd, Christchurch, New Zea
land.
Date Of issue
T830 Series II Preliminary Servlce Manual published August 1997
Copyright TEL August 1997
Changing the Operating Frequency of the T800 Series]!
Overview
“
Introduction When you receive the T800 module it will be run up and working on a par-
ticular frequency. Sometimes you may want to change the operating fre-
quency. In some cases, when you change the operating frequency, it will
also be necessary to re—lune the radio to ensure correct operation
“fi—
Purpose of this It is the purpose of this document to familiarise you with the procedures
document that must be carried out to check that the radio is still operating correctly,
and how to re-tune the radio when this is not the case
“—
In this section This section covers the following topics:
Topic See page
How to change the operating frequency 2
How to re—tune the T835 L 4
How to re-tune the T836/837 7
Configuring the Audio Processor 11
How to determine iflhe T835/836/837 is still operating 16
_—__—-—_—.—_
r lwu|30W.
Adjust RVBZU for the required output power (between 5 and 25W).
Readjust CV451 to reduce the supply current by up to 0.5A.
Copyright TEL ““ sum/95
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63.5 TESS/537 Initial Tuning 5 Adjustment Mezzo-cu
3.4.4 Two Point Modulation Adiusimeni
Note 1: In this and following sections deviation settings are given first for wide
bandwidth sets, followed by settings in brackets for mid bandwidth sets ( )
and narrow bandwidth sets [ ].
Natez: Reference modulation and limiter adjustment are controlled by
FGMBDOWin Electronic potentiometers (256 step) are used to allow chan-
nel~by-ehannel adjustment of deviation and two point modulation.
Note 3: To optimise the modulation response across the switching range. repeat
Nate:
3.4.5
Nuts:
steps 14 below for each channel that will be used (usually needed only for
data applications). In applications where the modulation response is less
critical (e.g. voice use only), carry out steps 1-4 below an the middle channel
and cut and paste the value to all other channels.
Inject an audio signal of 600Hz 1.5V rms (+5dEm) into the Cl'CSS input (D-range
1 (PL100)pi.n 8).
Key the transmitter by ear-thing the Tx-Key line.
Adjust the output from the audio generator to obtain tSkl-Iz (tZAkHz) [flskllz]
deviation at 600Hz.
Change the input frequency to 120Hz and adjust “reference modulation” via
PGMSOGWin to obtain zskl‘lz (zZslkl-Iz) [tLSkHz] deviation (you can use either
the mouse or up and down arrow keys).
Change the input frequency back to GOOHZ.
Repeat steps 2 and 3 above until the deviations achieved at the two input frequen-
cies are within 0.2dE of each other. You will need to do this at least four times.
Sweep the audio between 50 and 300Hz for peaks.
A peak between 513 and 300112 will indicate a fault condition, i.e:
- incorrect setup
or — modulation circuitry fault.
The specification window is zldB relative to 150I-Iz from 65 to 260112,
FM Deviation (Limiter) Adjustment
If the T836/837 will be used over the whole BMHz switching range, you
must set the deviation for each channel. However, if the module will be
used on frequencies that cover only a lMHz (or less) switching range, you
can set the deviation on the middle channel and use this value for all other
channels with the “fill” option in PGMSOOWin.
Inject lkHz at -ll)dBrn into the line input (D-range 1 (PLZOO) pins 1 & 4; pins 2 8: 3
shorted; refer to Section 2.2 of Part F).
30/04/95 Copyright TEL
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21 07 95 TLE 14:25 FA.\ 64 3 32394532 RSD , DEVELUP‘HT ‘008
Mswno Teas/537 Inillal Tuning E Adjustment (23.7
Adjust RVZlU (line sensitivity) fully clockwise and key the transmifler by earthing
the Tx—Key line. Adjust ”deviafion” via PGMBUOWin to set the peak deviation to
z4l7kHz ($3.8kHz) [12.3kHz] (you can use either the mouse or up and down
arrow keys).
Sweep the audio frequency from IOOHZ to 4kHz and ensure that the maximum
deviation does not exceed 4.7kI-lz (£3,8kHz) [2.3kl-Iz]. Readjuet ”deviation" if
necessary via PGMSOOWin.
3.4.6 LIne-In Level Adjustment
Set the injected signal at the line input to the required line level (typically -10 to
-20dBm).
Adjust RVZlD (line sensitivity) to provide tSkHz (zlAkHz) [21.5ka deviation.
Copyrighl TEL 30/04/98
2007 '95 TH; 14:22 FAA (N 3 1559-1532 RSI) — DELLUPHNT VlOfH
02.12 TESS/837 circuit Operation MESMO
-——
ID: CASTEL0004 -_
2.8 T8315 Drive Amplifier&PA ' 2.983 (d)(10) CIRCUIT DESC.
(Refer to Figure 2.1 and the exciter and PA circuit diagrams (sheets 3 k 4) in Section 6.2.)
The output power of the PA is maintained at a constant level via a power control loop
applied to the two—stage, wide band exciter amplifier (Q365, Q370). The forward and
reverse RF power levels are sensed via a dual directional coupler and detector diodes
(D410, D420 in the PA cavity). The detected DC signals are summed with the power
adjust' level and fed to the control integrator (IC330 pins 1, 2 8: 3). The output confl'ol
voltage is buffered by QBIU and Q315, and applied to the collectors of the wide band
exciter amplifier.
Note: Forward and reflected power signals are summed so that, under high
VSWR, the power control will turn the output RF level down.
To reduce the spurious output level when the synthesiser is outflf—lock, the Tx—Reg. and
Lock-Detect signals are gated to inhibit the PA control circuit and to switch off the RF
signal at the input to the drive amplifier. This is achieved by a PIN switch attenuator
(D340, D350, D360).
Cyclic keying control is provided by additional orniitry consisting of several time
delay, ramp and gate stages:
' Q350, 0355, 0360.1C330 pins 1, 2 6: 3 power ramping
' Q340, 0345 Tx-Reg. and Lock-Detect gate
- (2320, Q325, Q330, Q335 delay and PIN switch drive.
This is to allow the RF power circuits (both exciter and PA) to ramp up and down in a
controlled manner so that minimal adjacent channel interference is generated during
the transition.
The output of the wide band amplifier is approximately EOOmW (+27dBm) for an input
of 170mW (+22dBm) when the power conuol is set to maximum.
The zener diode (D330) limits the upper range of the controlled voltage to the exciter
transistors.
A temperature sensor (R450) is provided so that the RF output power can be reduced to
a preset level when a set temperature is exceeded. This is a protection circuit (IC330
pins 5, 6 8: 7, QBOS) to prevent overheating, as the unit is not rated for continuous oper-
ation at high temperatures (refer to Section 1.2.3 for duty cycle specifications). RV330
sets the PA output power while under high temperature foldvback conditions
R359, R360 and R362 form a 6dB attenuator to provide good VCO/exciter isolation.
The output attenuator (R392, R390, R394 and R396) aids in reducing exdter/PA interac-
tion while also ensuring a reasonable match for Q350.
The RF output from the exdter is fed to the driver stage (0415) and then to the final
(Q425). DC is fed to the final via a low pass filter with special low frequency decou‘
pling. CV451 tunes the output matching across the entire band.
30/04/90 Copyrighl TEL

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