Tait TEL0061 Paging Transmitter User Manual PagingBoardFitInstruction

Tait Limited Paging Transmitter PagingBoardFitInstruction

PagingBoardFitInstruction

8T800-32-0010 Fitting Instructions 419-83210-00 419-83210-00 T800-32-0010 Fitting Instructions 1Figure 8 Pinouts for D-Range 212345689102004f_01DATADATALock detectCoaxial socket(externalreferencefrequency)7T800-32-0010 Paging BoardThe T800-32-0010 PCB can be fitted to Tait T800 Series II transmitters to ena-ble them to function as low-speed paging transmitters. This paging board isfor transmitters that will be connected to an external frequency standard. It isa DFSK Modulator, suitable for POCSAG or similar paging data formats. Ref-erence frequency stability is determined by the stability of the external stand-ard. The PCB is not designed for use with 66 to 88MHz equipment. Newer T800 transmittters have a Micromatch connector in the audio proces-sor compartment. This simplifies installation. This fitting instruction describes how to fit the PCB into existing T800 trans-mitters. You need to be proficient in the soldering of SMD components. Itmay be preferable to obtain a T800 transmitter already fitted with this boardfrom your Tait dealer or national sales office. Parts RequiredThe T800-32-0010 kit should contain the following items:1 x T800-32-0010 DFSK modulator board1 x terminated coaxial cable1 x T800-03-1000 auxiliary D-range kit4 x M3 x 8 Taptite Pan Torx screws1 x coaxial socket1 x 47 ohm resistor SMD 08051 x terminated 8-way ribbon cable1 x terminated 4-way ribbon cableInstallationCaution: The radio must be powered off for this modification. After modi-fication, do not remove the coaxial lead from the socket unless theradio is powered off.1. Remove the TCXO module from the synthesiser compartment of theT800 transmitter.2. Fit the miniature coaxial socket (=SK710) and 47 Ohm SMD resistor (=R705) to the PCB pads provided beneath the TCXO, as shown in Fig-ure 1.
2T800-32-0010 Fitting Instructions 419-83210-00 419-83210-00 T800-32-0010 Fitting Instructions 7Figure 1 Location Of Socket And SMD ResistorNote: Keep the angle of the coaxial socket steep to ensure that there is space for theMicromatch 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 D-range with a second Micromatch socket can be fitted.)4. Remove R291, R289, and R296 from the audio processor (shown in Figure 2).Figure 2 T800 Transmitter Audio Processor (older version without Micromatch connector) - Top SideR291S6S7S5R289R2964. Using an AC-coupled oscilloscope set to 50 mV/div, observe the signal at TP2. Adjust RV2 until the triangle wave amplitude has been mini-mised.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 oscil-loscope set to at least 20 mV/div and 0.5ms/div. Vary the input fre-quency down to low frequencies (for example 100 Hz) and check that the control line still has a good square wave.Note: You may have to re-adjust RV2 and RV1 alternately to achieve a square waveon the VCO control line and a 4.5 kHz deviation. Figure 7 shows a typical 100Hz VCO control line waveform with RV1 and RV2 set correctly.Figure 7 100 Hz VCO Control Line WaveformNote: 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 squarewave displayed. Determine if this is a problem by directly monitoring theoriginal square wave source and observe any sag.If there is sag, switch the oscilloscope to DC and use a 10µF capacitor inseries with the scope probe (observing the correct polarity) to directly monitorthe VCO control line. Note that the trace settling time will be approximatelyone minute.
6T800-32-0010 Fitting Instructions 419-83210-00 419-83210-00 T800-32-0010 Fitting Instructions 3Figure 6 shows the location of these resistors on the PCB.Figure 6 Location of Zero Ohm ResistorsFor a different frequency, calculate the resistor pattern as follows:1. Divide the external oscillator frequency by 100 kHz.2. Convert the result into binary.3. Where there is a 0 in the binary number, place a zero ohm resistor in the equivalent position. Where there is a 1, leave an open link. Modulation AdjustmentBefore the paging transmitter can be used, its modulation must be set up cor-rectly.1. Apply +5 V DC to the DATA input (see Figure 8 for D-range 2 pinassignments) and observe the transmitter output using a frequencycounter. The output should read the carrier frequency. 2. Remove the +5 V DC from the DATA input and apply a ground ( 0 V) to the DATA input. Observe the transmitter output with a frequency counter. Adjust RV3 to get an output of Fcarrier + 4.5 kHz.3. Remove the 0 V from the DATA line and apply a 100 Hz 5 Vp-p square wave.MSB LSBN7 N6 N5 N4 N3 N2 N1 N0R92 R93 R94 R95 R96 R97 R98 R99RV392IC 14TP2999897969394955. Remove R718 and R719 from the synthesiser compartment (shown in Figure 3).Figure 3 T800 Transmitter Microntroller and Synthesiser Compartments6. Remove R841 and R842 (SMD) from the microcontroller compartment (shown in Figure 3) to disconnect the appropriate lines from the micro-controller.7. Lay the T800-32-0010 PCB above the exciter compartment with the component side up and positioned so that the Micromatch sockets are on the side closer to the front panel of the radio.8. Connect the 8-way ribbon cable to the SK200 Micromatch socket in the audio compartment and connect the other end to the Micromatch socket SK3 on the PCB. R718 R719R841 & R842
4T800-32-0010 Fitting Instructions 419-83210-00 419-83210-00 T800-32-0010 Fitting Instructions 5If there is no Micromatch socket in the audio compartment (olderSeries II transmitters), connect wires from the PCB to the audio com-partment as follows. For more information, refer to Figure 2 and the Test Points and OptionsConnections drawing in the relevant service manual)9. Connect the 4-way ribbon cable to the Micromatch socket SK4 and feed it through the loom channel cast into the chassis, to the auxiliary D-range compartment, as shown in Figure 4.10. Connect the coaxial cable provided between SK1 on the T800-32-0010 PCB and =SK710 on the T800 transmitter PCB, as shown in Figure 4.Figure 4 Cable Routing11. Screw D-range 2 in place.12. Thread the second coaxial cable from D-range 2 through the loom channel to the paging board and connect it to SK2.13. If the transmitter will be operating in VHF (frequencies <360 MHz), solder short LINK2 and LINK 3 (see Figure 5). (The T800-32-0010 PCB links are set for UHF operation.) Figure 5 T800-32-0010 Link Location - Top Side14. Turn the T800-32-0010 PCB over, so that the ribbon cables and compo-nents face down, and position it above the audio processor compart-ment.15. Connect the other end of the 4-way ribbon cable to the Micromatch socket on the auxiliary D-range.16. Screw the PCB in place using the 4 M3 x 8 screws provided.Configuring for the External Oscillator FrequencyThe PCB is configured for a 10 MHz external reference, using a pattern ofzero ohm resistors. For a 5 MHz or 12.8 MHz external oscillator frequency,you need the following pattern:Wire Length (mm) Connectionredgreyblack140140140S5 I/O Pad, P240 (+9V) just below D230S7 I/O Pad, P271 (BUFF_IN)S6 I/O Pad, P261 (GND)First coaxial cable4-way ribbon cableSK1 SK4AuxiliaryD-range(D-range 2)SK2Second coaxial cableReference Frequency Resistors5 MHz12.8 MHzR92, R93, R96, R97, R99R93, R94, R95, R96, R97, R98, R99RV2RV1SK4SK3LINK2 LINK3S7S6S5 S2S1S3S4RV3SK1SK2LINK192IC 14TP299989796939495

Navigation menu