Hi Scott,
You said "I have never seen broadband noise with 120 Hz harmonics
in the AM audio which was NOT power line noise. And, alas, I've seen a
lot of line noise."
I personally have experienced broadband noise (no peaks or valleys in the
RF spectrum over the entire 160 meter band and elsewhere as an example)
that often has 120 Hz harmonics that is not power line related and a
perfect example is the light dimmer in my family room. I actually use our
family room light dimmer circuit as a test bed for testing various antennas
and SDR software, and recently used it to test the new feature I had them
add to the TinySA (interval triggering so the triggering in zero span mode
would be in sync with 60 Hz as an example). My light dimmer generates so
much broadband noise that I can even hear it up on 146 MHz when I point my
portable VHF antenna at my family room.
I suspect most SCR circuits doing phase control on 60 Hz power will
generate similar noise if not properly filtered and an example besides
light dimming would be SCR phase angle control of resistance heaters which
we often use on our production equipment and these SCR phase angle control
units are fed directly from 60 or 50 Hz power depending on the country and
the risk of backfeeding high frequency harmonics onto the incoming power
lines is substantial unless adequate filtering is used.
I do use the audio spectrum waterfall (as well as the RF spectrum display)
to help eliminate power line noise as a potential source, but not to
confirm power line noise as a potential source, and the only reason I care
about eliminating power line noise as a potential source is that I then
typically leave my VHF DF gear in the car etc.
Just FYI and 73,
Don wd8dsb
On Wed, Feb 1, 2023 at 3:19 PM K9MA <k9ma@sdellington.us> wrote:
> On 2/1/2023 12:51 PM, Jim Brown wrote:
> > On 2/1/2023 4:52 AM, K9MA wrote:
> >> Besides the preponderance of 120 Hz harmonics in the AM audio, the
> >> very broadband nature of line noise is usually the main indicator.
> >
> > 120 Hz is also a strong component of electronic noise generated by
> > power supplies and power control equipment. The audio spectrum is not
> > a great clue -- the RF/IF waterfall shows where the bodies are buried.
> >
> > 73, Jim K9YC
> > _______________________________________________
> >
> That's true, but I have never seen broadband noise with 120 Hz harmonics
> in the AM audio which was NOT power line noise. And, alas, I've seen a
> lot of line noise.
>
> 73,
>
> Scott K9MA
>
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
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