Ramsey Electronics FM10A manual Circuit Description

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CIRCUIT DESCRIPTION

A quick glance at the Schematic Diagram shows that the custom FM stereo transmitter IC (U1) is at the heart of the FM10A. The control of U1 is determined by its surrounding circuitry. Potentiometers R1 and R4 allow for adjustment of input level. Resistors R3 and R6 set the pre-emphasis characteristics (75uS for USA and 50uS for Europe). R7 permits adjustment of stereo balance. L1 and C16 form an adjustable resonant circuit to set the carrier operating frequency. Diodes D1,2 and 3 regulate the voltage to U1 at

2.1volts DC, though Q1 may be operated safely up to 12-15 VDC. The RF output of Q1 feeds both the on-board whip antenna and J3 for an external antenna.

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Contents

FM Stereo Transmitter Partial List of Available Kits Ramsey Transmitter Kits Ramsey ELECTRONICS, INC Table of ContentsIntroduction Circuit Description Resistors Parts List CapacitorsSemiconductors Hardware and MiscellaneousOptional FM10A Parts Layout DiagramREQUIRED, not Supplied Building your FM10A Stereo Transmitter Assembly InstructionsFirst assembly steps Enough said. . . Lets get building Wiring the audio input circuits RF amplifier and final components Page Choosing AN Operating Frequency FM10A frequency range selectionDesired Transmitter Frequency Range C16 Value Transmitting Frequency Adjusting Your FM10A TransmitterAudio Connection Stereo balanceD. Power on Indicator Using the FM10A Within the HomePower Supply Considerations Experimental Broadcasting Projects Antenna Ideas Hints Troubleshooting GuideAntenna Alternatives Appendix a FCC Rules and Information Page Page Appendix B Understanding Legal Field Strength Why talk about acres? Lawful use suggestions for the FM10A SummaryImmediately Final comment Ramsey Kit Warranty Required Tools Estimated Assembly TimeAdditional Suggested Items Total Solder Points