Q: What are circulating ground loops and magnetic induction loops? What are their symptoms and how can I fix them?
A: Like a lot of things, when you get down to the details, there can be disagreement about certain matters.
Consider that the Super Chief manual states: "To minimize the possibility of radio interference, twist all conductors." Yet, this database has an article that states to the contrary; please see the related article in question, which is linked below. In this situation, it must be remembered that the original manual was written several years ago and the most recent update was in 2004 (and not every section was updated). The article, on the other hand, is the result of a direct question recently placed with A. J., so it should be considered as authoritative.
So, what to do? The Super Chief manual states:
"Circulating ground loops may cause problems with your DCC layout. We often see this on existing layouts that have been added on to over the years. If you are experiencing problems in a localized area of your layout, you may need to look for this problem and fix it."
"Wire the power feeds away from the boosters and command stations, in a radial “star like” configuration to minimize the possibility of creating “magnetic induction” loops."
To be honest, these statements may be overkill, as is the case with twisted feeders. What is being described would occur if you coiled up LocoNet or feeder wires into a loop, which might create inductive currents like the solenoid coil of a turnout motor. The best policy is to keep the wire runs relatively straight and as short as possible. And, of course, there's always the unaccountable problem, so it is helpful when laying out your wiring network to be able to isolate the various segments. If problems arise, you can then isolate the problem to a particular area and research it further.
In talking with others, the feeling is that interference rarely occurs, but it has been known to happen. The best approach is to be able to isolate it so that it can be solved.