Asked, "Does anyone know what the characteristic input and output impedances of the 220 9MHz filter are? Or the 6.3 MHz filters?" Duane N9DG Yes, I do! The input and output Z of the 220 is 200 ohms. The models 282, 285 and 288 are 6.3 mHz and have input and output Zs of 200 ohms also. 73, Roy K6XK