Ensemble RXTX Builders 1

Posted on Feb 7, 2014

The mixer stage (`QSD` - Quadrature Sampling Detector) acts like two traditional direct conversion mixers operating in tandem. Each takes in half of the filtered RF from the bandpass filter stage and one of the quadrature center frequency signals, then `mixes`/down-converts them to with an output being the traditional mixer products, in this case,

Ensemble RXTX Builders 1
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two (infra) audio frequency signals that represent the difference between the two inputs (RF and Local Oscillator). These two signals are referred to as the detected I (in-phase) and Q (Quadrature) signals and are fed into the high gain Op-Amps stage for amplification and delivery to the audio outputs (and, thence, to the PC`s sound card). The mixer is enabled by the QSD enable line, switched in the RF I/O Control Stage`s Q9. When the PTT line is activated, the QSD Enabling line goes high and disables the RX Mixer.

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