I'm reading about using software-defined radio for picking up ADS-B signals at 1090MHz. There is this blog which considers (among others) a setup as follows:
Antenna -> coax -> low noise amplifier (LNA) -> filter -> software-defined radio dongle
After that, it mentions swapping the LNA and the filter with the following note:
At some point a very strong "Blockers" signals will push any LNA into the saturation where IMD products will be created spoiling the reception. To avoid that, the filter should be placed in front the LNA protecting the system from the unwanted signals leaving only the targeted signal. Such a filtered signal is then amplified in the chain. Both the LNA and filter are close to the receiver (indoor).
I found that "IMD products" refers to intermodulation, but the blog is not detailed enough to go into the circumstances under which this becomes an issue. Since they mention both options, I assume there is some trade-off going on, possibly based on some of the following factors (these are just factors I can think of, there may be more and these may not be factor after all):
how well out of band signals are filtered out by the filter
how much the LNA amplifies in-band signals
initial signal to noise ratio
signal to noise ratio after the filter
Which of these factors play a role, and what's the theory behind choosing between the one option over the other? I'm aware that one can simply try both and compare the results in any specific setup, but I'm really looking for the theoretical idea behind it.