Z is input-impedance. This figure indicates the performance of the low pass filter. Single filter has -15db ratio in 94MHz. Double filter has -45dB performance. Each filter has very low loss on original 50MHz signal.
Frequency is measured by the counter.
Gain is measured by the oscilloscope after detection by 1N60 diode. I am confident of using these filters in my rig, after measuring the character by this way. As I find your circuits and ideas very interesting for my own experimenting in electronics and Ham radio, I had to come back and download them again. This time stored on a ZIP disk. I have built the UHF and VHF generators and am building up a Sweep Gen based on your circuit at present.