Interesting, Mike, and that thought crossed my mind, but if the S meter is
accurate, that is a 50 dB change. Have you really seen it be that much
different? It would be challenging to build a 50 dB attenuator from components
as big as power lines, so I didn't really consider that possibility with a 50
dB change.
________________________________
From: Michael Martin <mike@rfiservices.com>
Sent: Monday, January 29, 2024 4:53 PM
To: Hare, Ed, W1RFI <w1rfi@arrl.org>
Cc: RFI@contesting.com <rfi@contesting.com>; Wes Stewart <n7ws@yahoo.com>
Subject: Re: [RFI] Mystery Noise (Aren't they all)
It's very common to see the noise level drop when turning off the main because
you have just disconnected a large portion of the antenna which will weaken the
signal. It's possible the noise source is the same just a lot weaker because of
reducing the antenna size. You have also disconnected the physical connection
between the wires in the house and the wires outside of the house. Any noise
coming in through the house and into the radio via the wiring would be
disconnected. I often have clients that call me from a customer's house telling
me the ham has 20 over noise level but they see nothing on their RFI equipment.
I tell them to connect the receiver to the house power and it totally changes
the level of noise they receive when their battery powered equipment.
Michael Martin
RFI Services
51 W Bay Front Rd
Lothian, MD 20711
240-508-3760
mike@rfiservices.com<mailto:mike@rfiservices.com>
www.rfiservices.com<http://www.rfiservices.com>
On Mon, Jan 29, 2024, 6:52 AM Hare, Ed, W1RFI via RFI
<rfi@contesting.com<mailto:rfi@contesting.com>> wrote:
<In conversation with the tech a few days ago I offered to battery power my
TS-890 and turn off the whole house breaker. When I did the noise went from
S9+10 dB down to about S4, but it was still there! >
What you are hearing at S4 is either a different noise source, or even the
ambient noise levels present in typical residential environments.
Re-energize the main breaker, but turn off every other breaker in the house.
Then, turn them on one at a time and note any increase in noise level. If the
noise goes up significantly, it is likely that there is a noisy device in your
own home. Next, turn the breaker to that circuit off and turn on the next
breaker. You want only one breaker at a time turned on at a time because there
could be multiple devices in your home generating noise.
That S4 noise could either be the ambient noise in your neighborhood from the
aggregate of many devices or even coming in by skywave. At most locations, on
the lower bands, at night, an S4 noise level would be pretty typical.
Even if the S4 noise is coming from a local source, it is not likely that the
utility would be able to locate it. It might be coming from some distance away.
If the specific source can be identified, you may be able to get the utility
or operator of the noisy device to address it.
At S4, it is not likely that the FCC will take any specific action. On the
lower bands, the median levels of human-made noise are typically S6 in most
residential environments and the FCC generally does not act for noise levels
below what most residential environments endure. Keep that in mind as you may
negotiate with the operator of the device generating that S4 noise (assuming is
not just the ambient noise from no specific device).
Ed Hare, W1RFI
________________________________
From: RFI
<rfi-bounces+w1rfi=arrl.org@contesting.com<mailto:arrl.org@contesting.com>> on
behalf of Wes Stewart via RFI <rfi@contesting.com<mailto:rfi@contesting.com>>
Sent: Sunday, January 28, 2024 10:50 PM
To: RFI@contesting.com<mailto:RFI@contesting.com>
<rfi@contesting.com<mailto:rfi@contesting.com>>
Subject: [RFI] Mystery Noise (Aren't they all)
I have been plagued for months with raucous noise, primarily on 160-meters. Our
power co-op has a tech who maintains their com gear and fills in as their RFI
guy. I gave him a plug at a meeting with the CEO and suggested that he needed
better equipment. So he has the latest Radar Engineers 243, ultrasonic dish,
etc. But he's struggled to find this particular noise and I finally got him
into my shack and connected to my antenna, which pegged his meter and gave him
a signature.
The problem with this organization is if he finds a suspect, he has to request
a line crew which usually shows up when he's not around. That was the case
here; he identified a pole, they came out later and said they didn't find
anything. This was all unbeknownst to me and a few days later I happily
reported the noise was gone. He said, "Huh, that's funny, they said they
didn't fix anything." Of course, it came back.
It has a strong 120 Hz component, but overlayed on that is a lower frequency
modulation that is frequency sensitive. In other words, if I tune for example
to 1830 kHz I might hear the low frequency noise (Which I have dubbed rotating
machinery) and then tune just +/- 10 kHz the low frequency stuff goes away and
I'm left with the background stuff.
In conversation with the tech a few days ago I offered to battery power my
TS-890 and turn off the whole house breaker. When I did the noise went from
S9+10 dB down to about S4, but it was still there! I re-energized the house
but opened the breaker to the shack and the noise was the same as with the
whole house turned off.
I have limited test equipment these days. In addition to the shack transceiver
I have a Sony ICF-SW7600GR, which with just a loopstick antenna, has proved to
be nearly worthless, and a TinySA Ultra, that I haven't tried.
This place has a smart meter which radiates prodigious garbage within a couple
feet or so on the Sony RX on several bands, but falls off rather quickly with
distance. The RFI guy has suggested that I get a meter maid out here to pull
the meter while I run further tests.
Any other suggestions?
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