Tait TEL0061 PagingBoardFitInstruction

8 T800-32-0010 Fitting Instructions 419-83210-00 419-83210-00 T800-32-0010 Fitting Instructions 1

T800-32-0010 Paging Board

The T800-32-0010 PCB can be fitted to Tait T800 Series II transmitters to ena­ble them to function as l ow-speed paging tran smitters. This pagin g board is
for transmitters that will be connected to an external frequency standard. It is
a DFSK Modulator, suitable for POCSAG or similar paging data formats. Ref­erence frequency stability is determined by the stability of the external stand­ard. The PCB is not designed for use with 66 to 88MHz equipment.

Newer T800 transmittters have a Micromatch connector in the audio proces­sor compartment. This simplifies installation.

This fitting instruction describes how to fit the PCB into existing T800 trans­mitters. You need to be proficient in the soldering of SMD components. It
may be preferable to obtain a T800 transmitter already fitted with this board
from your Tait dealer or national sales office.

Parts Required

The T800-32-0010 kit should contain the following items:

1 x T800-32-0010 DFSK modulator board
1 x terminated coaxial cable
1 x T800-03-1000 auxiliary D-range kit
4 x M3 x 8 Taptite Pan To rx screws
1 x coaxial socket
1 x 47 ohm resistor SMD 0805
1 x terminated 8-way ribbon cable
1 x terminated 4-way ribbon cable

DATA

DATA

Lock detect

1

7

2

8

3

4

9

5

10

6

Figure 8 Pinouts for D-Range 2

Coaxial socket
(external
reference
frequency)

2004f_01

Installation

Caution:

1. Remove the TCXO module from the synthesiser compartment of the

2. Fit the miniature coaxial socket (=SK710) and 47 Ohm SMD resistor

The radio must be powered off for this modification. After modi­fication, do not remove the co axial lead f rom the so cket unle ss the
radio is powered off.

T800 transmitter.

(=R705) to the PCB pads provided beneath the TCXO, as shown in Fig­ure 1.

2 T800-32-0010 Fitting Instructions 419-83210-00 419-83210-00 T800-32-0010 Fitting Instructions 7

4. Using an AC-coupled oscilloscope set to 50 mV/div , observe the signal
at TP2. Adjust RV2 until the triangle wave amplitude has been mini­mised.

5. Apply 600 Hz to the DATA line. Use a modulation analyser to observe
the frequency deviation on the output of the transmitter . Adjust RV1 to
get 4.5 kHz deviation on the modulation analyser.

6. Observe the transmitter’s VCO control line using an AC-coupled oscil­loscope set to at least 20 mV/div and 0.5ms/div. Vary the input fre­quency down to low frequencies (for example 100 Hz) and check that
the control line still has a good square wave.

You may have to re-adjust RV2 and RV1 alternately to achieve a square wave

Note:

on the VCO control line and a 4.5 kHz deviat ion. Fi gure 7 show s a typical 100
Hz VCO control line waveform with RV1 and RV2 set correctly.

Figure 1 Location Of Socket And SMD Resistor

Keep the angle of the coaxial socket steep to ensure that there is space for the

Note:

Micromatch cable as well as for the coaxial cable.

3. Remove the two screws and cover plate from the second D-range
mounting hole at the rear of the T800 chassis. (If the transmitter
already has a second D-range, this must be removed so that the D­range with a second Micromatch socket can be fitted.)

4. Remove R291, R289, and R296 from the audio processor
(shown in Figure 2).

Figure 7 100 Hz VCO Control Line Waveform

S5

S6

R291

S7

R289

R296

Figure 2 T800 Transmitter Audio Processor (older version without Micromatch connector) - Top Side

If the lower cut off frequency of an AC coupled oscilloscope is too high,

Note:

excessive distortion may be introduced which will result in 'sag' on the square
wave displayed. 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 th e trace settling ti me will be ap proximately
one minute.