If you are throwing together a quick analogue filter, I used to use this site for RF filter design: https://www.changpuak.ch/electronics/index.php#
But I just found this one, which looks like a lot of fun: https://rf-tools.com/lc-filter/
I tried it with the following:
Response: lowpass
Type: Butterworth
Topology: Series First
Order: 5
Cutoff Frequency: 60MHz
Input Impedance: 50 ohms
Output Impedance: 50 ohms
Component Values: Standard
Capacitor Values: E24 (5% tolerance)
Inductor Values: E24 (5% tolerance)
The only thing that it is missing is a Monte Carlo plot, for the random values with 5% tolerance of the components I selected.
EDIT: Under export there is an option to select Monte Carlo for analysis in LTSpice!
The thing about SDR is that there is a lot of complexity, and explaining what looks like a simple problem gets hard fast. And I’m no expert, I’m still learning.