Placeholders of images I'm about to upload.

Channel 1 (yellow) is the low pass filtered output. Channel 2 (blue) is the output at the final 3 dB pad after the second mixer.

In all cases, there is a lot of noise appearing at channel 1 for a currently unknown reason, possibly poor LPF design.

NewFile1 - no power applied to receiver.

NewFile0 - input is a 50 R terminator. Channel 2 displays (what looks like) reasonably little noise. Here there is no filtering at all, including bandwidth limiting on the DSO.

NewFile2.bmp and NewFile0.wfm - 50 R terminator and 20ns/div, showing channel 1 noise (the 50 MHz LO)

Measuring gamma (beta l) along the coax cable to the antenna:

dataset.004 - short circuit at antenna end 005 - open circuit