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 (onboard jumper selectable), see pictures
above. 1.8MHz-28MHz insertion loss is about 0.5 dB or less. 50 MHz band
insertion loss is 0.8dB. 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 30 dB for 1.8MHz-28MHz and 28dB for 50 MHz.
Maximum handled power for any band is 100w with 50% duty cycle with no external
cooling, 100% duty cycle with air colling.
Only high quality and original components using – AMIDON T68 and T50 cores,
and NP0 Hi-Q, low ESR RF capacitors. SWR and ferrite rings temperature should
be under control.
Board size is 149 x 110 mm.
Power supply – 12v 0.2A max