a. Think the 3 ft radio-to-75 ohm patch cable, then to the 50 ohm main
cable will cause any "meaningful" loss
due to the Z mismatch ?

b. Would I have been better off using a 3 foot RG58 (50 ohm) patch
cable,
even though the RG58 is really lossy around 1 GHz ?

Thanks,
Bob

Bob,
I wouldn't sweat either issue; the loss in 3 feet or the impedance.

Howard

I agree, either way the loss of 3 feet of coax is not worth worring about.
Use whatever you can find.
Even replacing the entire 50 feet of coax with something like the rg-6 that
is in big supply now will probably not be noticed.