Скачать или смотреть Homebrew 80m/20m SSB Rig Part 2 - Crystal Filter

Ladder crystal filter using four 8MHz crystals. 9MHz would have been a better choice, but these were all I had on hand. I will look to initially use a 4.1-4.5MHz VFO for 80m. If this turns out to be problematic as 4.1MHz is quite close to the upper end of 80m, then I'll switch to high side VFO injection and use 11.5-11.9MHz.

Please note that I have elected to use a simplified method for the construction of this filter (right or wrong) and have not used specific filter design software. I tried that in the past with little success.
The -3dB bandwidth is approx. 1700Hz
Uses Excel to plot the passband response.
We'll see how this performs in the circuit and go from there.