Rev0VTx Modulator

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This page describes the 5.5 MHz Audio Subcarrier AM Modulator for the rev0VTx video transmitter.

Summary

Schematic for the rev0VTx Mod.
Board for the rev0VTx Mod.

The modulator is based on the topology used in the HobbyKing 900 MHz Video System. The design uses two BC817 (or similar) NPN BJTs, with a series resonant circuit made of a 10uH SMT inductor and variable/fixed capacitor. The first transistor forms the oscillator, and is amplitude modulated by applying the ~1-2Vp-p audio signal to the collector. A second transistor amplifies the modulated carrier. The board runs from a single 5V supply. The design was simulated and evolved in LTSpiceIV, using the built-in BC817 model. The Spice circuit for simulation can be found here: http://www.rev0proto.com/files/rev0VTx_MOD_Sim.asc The gerbers, Eagle schematic and board file can be found here: http://www.rev0proto.com/files/rev0VTx_MOD.zip

5kHz Audio modulated 5.5MHz carrier as simulated in LTSpiceIV.

Testing

PCB/Construction Photos