[John Williamson]

On 06/09/2018 19:23, Mike Rivers wrote:
On 9/6/2018 1:02 PM, John Williamson wrote:
If the interference is from a cell tower a block away, then it is RF

RFI is a special case of EMI. They're both electromagnetic radiation.
What you get from a power line or a wall wart is interference from
electromagnetic induction.

Picky, picky.

Not really. What I call EMI is usually low frequency, directly induced
in the coils, while RFI is a modulated higher frequency, which normally
only affects circuits with a semiconductor or other rectifying component
in them, such as a preamp.

I find it a useful distinction to draw, as the cures are different.

The OP describes a hum or a buzz, rather than the typical "chirping"
sound of a cellphone being picked up, so I was guessing at LF, possibly
from a choke, fluorescent light or (Unlikely) a SMPS near the
microphone, which doesn't have a humbucking coil. It's hard to get
interference from cellphone transmissions, even from base stations,
more than a few feet from the microphone due to the low power and
inverse square law of propagation, though an experienced movie sound guy
can often tell what make of cellphone is about to ring on set.....


--
Tciao for Now!

John.