Like you said, someone may already know, if you hear it, someone else
may hear it. If so, that's awesome. If not...
Lets start with exact frequency (ies), or overall range, then reception
mode, type of receiver, antenna used, power source, and if wide spread,
if possible to what extent, a square mile, 20 square miles, limited to
specific areas? Is it stronger at any particular spot? Get some
recordings to provide to some persons direct as they can't be passed
through the list.
Some will say RFI can't be ID'd by description, or sound, but those that
have been around, or even just heard a few types, can do just that, as
most RFI is unique to a large extent. A switching mode supply is unique,
the model number of consumer garbage it's installed in isn't, but nobody
will ever confuse it with the ignition system in a car, or even a power
line or wireless weather station, so a thirty second recording can rule
out literally billions of RFI sources across the US.
It may be local to you, may even be your own receiver, or power source,
or what you're using to move around to hear the signal all over the
place. Have you heard the signal on foot, with a battery powered
receiver, away from everything? To rule out a receiver, have you heard
it to the same extent with an entirely different receiver and different
power source?
Do you have any other electronics on your person at the time? I've
heard mobile phones, WiFi, Bluetooth, digital cameras, MP3 players,
near-field devices, like contactless payment devices, and transponders,
the type of stuff a person may normally carry. Even a digital recorder
I used to use wiped out a large frequency range from HF to UHF, so I use
an analog cassette recorder to document RFI.
You did mention 440. Any chance you are listening around 433/434 MHz?
If so, there is an ISDM (industrial, scientific, data, medical) band
there, and you will hear noise/telemetry, pretty much everywhere around
those frequencies, pretty much anywhere in the US. The devices are
supposedly limited to 300', but I hear them miles from the source, even
so far out in the desert, or hills, sources can't be seen.
Any radar installations in your region? 440 is also a military radar
frequency range, and I sometimes get blasted. The PAVE/PAWS system on
the west coast, for example, operates from 420-450 MHz, and wipes out
individuals, repeater, links, you name it, and I even hear it direct a
few hundred miles east of it on occasion. From the late 80's to late
90's, 420-430 MHz in southern california was often affected by several
radar systems.
Any extra information can help.
Kurt
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