Full-color, full-resolution graphics from the pages of QRP Homebrewer
QHB #9 -- November 2002
Low Pass Filters for QRP Transmitters, by Phil DeCaire, WB7AEI |
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3 element Butterworth filter with a cutoff of 9 MHz |
5 element design below shows a loss of only 0.4 dB with an input impedance of 37 +j21 ohms at 7.04 MHz |
If you need more harmonic attenuation for a given cutoff frequency, add more elements. Shown below is a 7 element 0.1 dB ripple Chebyshev low pass filter for 40M |