As a urban ham (Harvard Square, Cambridge MA), I'm on the hunt for RFI rejecting antenna configurations. After hours of research, I've come across many strong recommendations for loop antennas, since they supposedly respond less to electric fields. In reviewing my options, I see there are several different classes of these antennas such as:
Passive loop antenna such as the well loved W4OP (store link, eham review) - these often have a variable capacitor tuner with an apparently high Q which supposedly helps with noise rejection. (I suppose this avoids RFI on adjacent bands that would somehow swamp or add noise to the region you're interested in? But why would that be the case at all?)
On further digging, the major advantage of an active antenna would seem to be amplification that pushes signals over the line loss of the cabling. That hardly seems to account for the field reports that active antennas are somehow better at noise rejection.
My question - what is really the best approach for noise rejection in an RFI-washed space (easily 100 families within a 2 minute walk)? Which approach actually provides the best SNR? Does the pre-amp perform some other function that makes up for the apparent lack of tuner? Why don't we see active loop models that also tune? And why does the tuning on the passive loop help reduce noise?