Ensemble II VHF RX rf

  
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This stage begins at the VHF antenna. The incoming VHF RF signal is preamplified and filtered and presented as the `RF` signal to the ADE + Double Balanced Mixer (DBM). That mixer also accepts the Local Oscillator `s output (BEFORE the Quadrature Clock Generator ) as the `LO` input. The two signals, `RF` and `LO` are then mixed to result in the `I
Ensemble II VHF RX  rf - schematic

F" output of the DBM. This output contains the sum and difference products of mixing the two inputs. The sum component is filtered out, sending the difference component into the Quadrature Sampling Detector (QSD) stage. For example, assume that the VHF signal of interest is at a frequency of 145. 200 MHz. Thanks to the firmware in the on-board microcontroller in the LO stage, the LO will produce an output of 116. 16 MHz. The DBM accepts the preamplified and filtered incoming RF signal at 145. 200 MHz along with the LO signal of 116. 16 MHz, to produce a signal with sum and difference components: The sum ( £) is discarded and the difference ( ” = 29. 04 MHz) is sent to the QSD stage. If the SDR software was configured to set the center frequency at 145. 200 MHz, then it would manifest itself in the QSD as 29. 04 MHz.



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