7th order Chebyshev HF/6M 20W Low Pass Filter



This is a 7th order Chebyshev Low Pass Filter for using after HF power amplifier for removing harmonic. This LPF intended for HF amateur bands – 1.8 MHz, 3.5 MHz, 7.0 Mhz, 10 MHz, 14 MHz, 18 MHz, 21 MHz, 24 MHz, 28 MHz and 50MHz. 3dB cut off frequency is  2.5 MHz, 5 MHz, 8.6 MHz, 15.5 MHz, 25 MHz, 35 MHz and 55 MHz. You can choose cut off frequency by setting up binary code with 3.3v or 5v logic levels, see pictures above. All bands insertion loss is less than 0.5 dB. You can see attached graths  for exact, per bands, values. Input and output impedance is 50 Ohm. Input and output connectors is SMA female. LPF Return Loss is better than 35 dB  for any band. Maximum handled power for any band is 20W сontinuously, 40w with 30% duty cycle is ok too

Only high quality and original components using – AMIDON T50 cores, TAKAMISAWA relays, and  Hi-Q capacitors. SWR and ferrite rings temperature should be under control.  Board size is 120 x 75 mm

Additional information

Weight 0.110 kg


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20W LPF schematic diagram


20W LPF wiring diagram