D T800/T800 SERIES 2 MANUALS/Paging/T800 30 FITTING INS/T800 Inst. (Paging) T800

T800/T800 SERIES 2 MANUALS/Paging/T800-30 FITTING INS/T800-30 fitting inst. (Paging) T800-30 fitting inst. (Paging)

T800/T800 SERIES 2 MANUALS/Paging/T800-30 FITTING INS/T800-30 fitting inst. (Paging) T800-30 fitting inst. (Paging)

T800/T800 SERIES 2 MANUALS/Paging/T800-30 FITTING INS/T800-30 fitting inst. (Paging) T800-30 fitting inst. (Paging)

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4T800-30-0000 Fitting Instructions 419-83000-00 419-83000-00 T800-30-0000 Fitting Instructions 1
3. Change the audio generator frequency to frequency 1 and adjust RV3 (reference deviation
speech) on the T800-30-0000 PCB to obtain ±3kHz [±1.5kHz] peak deviation.
4. Change the audio generator input frequency back to frequency 2 and repeat steps 2 and 3 until
the deviations achieved at the two input frequencies are within 0.2dB of each other.
You will need to do this at least four times.
Data Modulation Adjustment
1. Inject a 100Hz 1:1 square wave into S4 of the T800-30-0000 PCB (D-range 2 pin 13) of at least
5Vp-p, to simulate a data input.
2. Monitor the carrier FM with a modulation meter via a suitable attenuator (if necessary), and
observe the modulation level.
3. Monitor the control line of the VCO (pin 1 on the VCO PCB) with an AC coupled oscilloscope
set to a sensitivity of at least 20mV/div with the time base set to 2ms/div.
4. Adjust both RV1 (VCO modulation) and RV2 (reference modulation) on the T800-30-0000
PCB to achieve a flat topped square wave on the oscilloscope, corresponding to ±4.5kHz peak
on the modulation meter.
You may need to repeat this procedure several times.
Figure 5 shows a typical 100HZ VCO control line waveform with RV1 and RV2 set correctly.
Note: Be aware that if the lower cut off frequency of an AC coupled oscilloscope is too high,
excessive distortion may be introduced which will result in 'sag' on the square wave dis-
played. Determine if this is a problem by directly monitoring the original square wave
source and observe any sag.
If there is sag, switch the oscilloscope to DC and use a 10µF capacitor in series with the
scope probe (observing the correct polarity) to directly monitor the VCO control line. Note
that the trace settling time will be approximately one minute.
Figure 5 100Hz VCO Control Line Waveform
DATA/SPEECH Input
With S6 low, data mode is enabled. If no data is present, the DFSK modulator defaults to speech
mode. However if S6 is high, only speech mode is enabled, regardless of the presence of data.
Introduction
The T800-30-0000 is a DFSK Modulator for T800 transmitters, suitable for POCSAG or similar
paging data formats. Analogue transmissions (e.g. tone or speech) are still possible by disabling the
data path with control line S6. 512 or 1200 baud data rates are link selectable and reference fre-
quency stability is ±2.5ppm from -30oC to +70oC. The T800-30-0000 PCB is not designed for use
with 66 to 88MHz equipment.
Parts Required
The T800-30-0000 kit should contain the following items:
1 x T800-30-0000 DFSK modulator board 1 x terminated coaxial cable
1 x T800-03-0000 auxiliary D-range kit 4 x M3 x 8 Taptite Pan Torx screws
1 x coaxial socket 4 x cable ties
1 x 47 ohm resistor SMD 0805 3 x cable clips
Installation
Caution: The radio must be powered off for this modification. After modification, do not
remove the coaxial lead from the socket unless the radio is powered off.
Figure 1 Location Of Socket And SMD Resistor
2. Remove the two screws and cover plate from the second D-range mounting hole at the rear of
the T800 chassis.
3. Remove C263 and R296 from the audio processor (shown in Figure 2), and clear the holes of
solder.
Figure 2 T800 Transmitter Audio Processor - Top Side
Remove C263 and R296.
1. Remove the TCXO module from the synthesiser com-
partment of the T800 transmitter.
Fit the miniature coaxial socket (=SK710) and 47
Ohm SMD resistor (=R705) to the PCB pads provided
beneath the TCXO, as shown in Figure 1.
Note: Keep the angle of the coaxial socket steep to
ensure that there is space for the Micromatch
cable as well as for the coaxial cable.
2T800-30-0000 Fitting Instructions 419-83000-00 419-83000-00 T800-30-0000 Fitting Instructions 3
4. Remove R841 and R842 (SMD) from the microcontroller compartment to disconnect the appro-
priate lines from the microcontroller.
5. Lay the T800-30-0000 PCB above the exciter compartment with the component side up and
positioned so that the wires are facing the front panel of the radio.
Twist the yellow, green and blue wires together and secure with the cable ties provided.
Route the wires and coaxial cable via the loom channel cast into the chassis to the synthesiser
and D-range compartments as shown in Figure 3. Depending on the chassis type, there will be
either holes in the chassis through which to pass the wires, or slots in the top of the chassis
walls. If the wires are passed through slots, use cable clips to hold them in place.
Pass the three wires through the D-range hole and connect to the auxiliary D-range plug
(D-range 2) as follows:
Figure 3 Cable Routing
6. Screw D-range 2 in place.
7. Connect the wires from the T800-30-0000 PCB to the audio processor as follows (refer to Fig-
ure 2 and the Test Points & Options Connections drawing in the relevant service manual):
Wire Length (mm) Connection Signal
yellow
green
blue
370
370
370
S4 pin 13
S5 pin 8
S6 pin 14
DATA
GROUND
DATA/SPEECH
Wire Length (mm) Connection
brown
red
orange
purple
grey
white
150
140
190
100
150
205
S1 I/O Pad, P275 (POCR) between C295 and IC210
S2 positive side of C263
S3 negative side of C263
S7 I/O Pad, P240 (+9V) just below D230
S8 I/O Pad, P273 (POCI)
S9 I/O Pad, P261 (GND)
S6
S5
S4
Coax
yellow, green & blue wires
SK1
auxiliary D-rang
e
(D-range 2)
8. The T800-30-0000 PCB links are set for UHF operation and 512 baud data rate. For the loca-
tion of the PCB links refer to Figure 4.
For 1200 baud rate, solder short LINK2.
For VHF operation, solder short LINK3, LINK4 and LINK5.
Figure 4 T800-30-0000 Link Location - Top Side
9. Connect the coaxial cable provided between SK1 on the T800-30-0000 PCB and =SK710 on the
T800 transmitter PCB, as shown in Figure 3.
10. Position the T800-30-0000 PCB above the audio processor compartment, with the wires and
components facing down.
Screw in place using the 4 M3 x 8 screws provided.
Adjustment
For speech modulator and data modulation adjustment with a T800-30-0000 DFSK modulator PCB,
carry out the following instructions instead of the audio processor modulator adjustments in Section
3 of the service manuals. Carry out the limiter adjustments as described in the service manuals.
During adjustment do not provide an input on the DATA/SPEECH terminal (S6).
The audio test frequencies used are as follows:
Note: Deviation settings are given first for wide band radios, followed by settings for narrow band
radios in brackets [ ].
Speech Modulator Adjustment
1. Inject an audio signal of frequency 2 at approximately +5dBm (1.4Vrms) into the CTCSS input
(D-range 1 pin 8) and earth the key line.
2. Adjust the audio generator output to obtain ±3kHz [±1.5kHz] peak deviation at frequency 2.
Transmitter Frequency 1 Frequency 2
T836/7
T856/7
120Hz
100Hz
600Hz
300Hz
LINK12
LINK11
LINK10
LINK9
LINK8
LINK7
LINK6
LINK1
LINK3
LINK5
RV2RV1RV3
TP4
TP2
TP3
TP1
LINK4
LINK2
S1S2S3S4S5S6S10S7S8S9

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