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8640Jr – Band 4 Low Pass Filter


8640Jr – Band 4 Low Pass Filter

There is a little distortion on the waveform of the Band 4 Low Pass Filter Output. The Spectrum Analyzer shows only about 14 db of attenuation on the 3rd harmonic of frequencies near the low end of the Range. This agrees with the predicted results below.


Band 4 Filter Passband

The original design looks like this…


W7ZOI Band 4 Lowpass Filter Schematic

The actual spectrum output looks like this on the low end of the range…

Spectrum Analysis of Band 4 Filter Output - Low end of Range

Things look better on the high end of the range, and the waveform looks better there, as well.

Band 4 Low Pass Filter Output - High End of Range

The predicted bandpass is as follows (21 mhz down about 12 db):


Band 4 predicted bandpass

Here are the waveforms… For the Low End Frequencies:


Band 4 Waveform - Low end of Range

and for the High End…


Band 4 waveform - High end of Range



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