Of course the real point is that EMI is not magnetic field. Which is
what my original post was addressing. I.e., that shielding is effective
for RFI/EMI but not for either external magnetic fields such as those
produced by transformers or induced magnetic fields such as produced by
current running through cables and wires. I used to work on the ELF
program which transmits at 75 Hz so yes, I’m quite familiar with low
frequency radio frequencies. Just because some people might not consider
it a radio frequency it actually IS a radio frequency.
Hi, atmosphere, sorry but no it’s not. EMI is radio frequency
interference just like RFI. It’s an electromagnetic wave. Unlike its
ugly cousin magnetic field which is a stationary field. Both EMI and RFI
are light speed. The other difference obviously is what I'm referring
to is the induced mag field whereas EMI is an external radio frequency
interference. I trust my post doesn’t sound too much like I’m all jacked
up on cafe lattes.
Its apparent to me that you did not look at the Wikipedia link I posted earlier for your convenience. EMI really is a magnetic field and one that can occur at almost any frequency. So is RF, as they originate from the same principle of electricity. We usually use 'RFI' to refer to higher frequency phenomena (an example might be an oscillation in a circuit) but its just a polite nomenclature. What is generally different about the two is that for audio purposes, RFI **usually** originates via an antenna (driven by an RF source), whereas EMI generally does not (likely instead radiates from a power transformer or power lines, or any source that is powerful enough to radiate directly without the need for an antenna, although power lines might well be argued to be antennae.
I recommend you take a look at the link I posted or ask your colleagues at the ELF station.
