transceiver circuits


Posted on Feb 4, 2014

The unit is based on a PHILIPS FM880 link transceiver which was originally supplied to a Telecom Australia specification for telephone applications in remote areas of Australia. The FM880 in turn is part of the family of equipment including the PHILIPS FM828/FM814 series of fixed and mobile transceivers. The main receiver and transmitter exciter b


transceiver circuits
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oards are identical in most cases and are surrounded with specialized boards and circuitry for the particular application. The VK6WIA modifications are therefore simply another variant of the versatile PHILIPS design, although a fundamental change has been made in that the system of modulation has been changed to direct FM of the exciter reference crystal oscillator. The inbuilt phase modulator on the original FM880 exciter board is unused. Other audio, power supply and control facilities have been added to provide the WIA Broadcast Officer with a transceiver designed to provide the regular news broadcast service. Extracts from the FM880 handbook, detailing receiver and transmitter circuit description, alignment instructions, circuit diagrams and board layouts are attached at Appendix I. 4. 1. Apply 13. 8 Volts to rear connector, connect antenna and attach microphone. Set all controls to max anticlockwise and toqqle switches to OFF (up). The DTMF / HL / Tone Switch should be on "HL". 4. 3. Advance Receiver AF gain by a small amount. Rotate Receiver SQL control until noise is heard. Set AF gain for a convenient level and adjust SQL for muting threshold. 4. 5. Advance the MIC gain and speak into the microphone without activating the PTT or TRANSMIT key. The microphone audio level should indicate on the VU meter. Set the MIC gain so that at the speaking level and distance to be used the VU meter on frequent peaks deflects to...




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