I tend to agree, although Ethernet wiring, if properly installed, seems to be
reasonably well balanced and does not radiate significantly... usually.
I have said this before, but it bears repeating here:
Part 15 rules require the following:
* Radiated emissions limits for a device or system must be met above 30 MHz.
* Conducted emissions onto the AC mains must be met below 30 MHz
* There are no specific emissions limits on conducted emissions onto other
wiring below 30 MHz. This point it critical, because for physically large
systems, such as the Ethernet wiring in a home, devices themselves (such as the
bulbs in question or the power supply providing power to the controller) do not
generally radiate on HF, but those wires do, and under Part 15, there is no
limit to the amount of signal or noise that can be conducted onto that
secondary wiring.
* The manufacturer must meet these limits
* There is an additional requirement that the device be used in a way that
does not cause harmful interference, but this is the responsibility of the end
user, not the manufacturer.
In ARRL's testing and case experience, these types of devices typically do
meet the emissions limits, with most noise not coming from the AC mains. For
solar systems, for example, all of our testing suggests that the manufacturer
meets these rules, which is the reason that ARRL is working quietly with
manufacturers, not trying to get resolution with the FCC as long as the
manufacturers are reasonably trying to resolve issues.
Now, Ethernet-controlled lighting will have similar issues, with one notable
exception: In solar, there are maybe 6 major manufacturers. With consumer
electronics, we are going to see a large number of manufacturers, rebranding,
imported products and many, many points of sale. And, if our past experience
is correct, many devices will meet the rules, but some will not.
Even devices that "meet the rules" can and do cause interference. The rules are
pretty lax, seemingly created with the idea that the rules should limit the
number of interference problems to a low-enough number that it is practical to
address them on a case-by-case basis. The limits also limit the geographical
area over which interference is possible, so if there is interference from a
legal system, it will be local and easier to find, not coming from a mile away.
Just some ramblings from the ARRL Lab volunteer. 🙂 FWIW.
Ed, W1RFI
________________________________
From: John Langdon <WOYB10051@outlook.com>
Sent: Thursday, August 24, 2023 5:17 PM
To: Hare, Ed, W1RFI <w1rfi@arrl.org>
Cc: : rfi@contesting.com <rfi@contesting.com>
Subject: RE: [RFI] LED Street lights
Ed,
I had an interesting discussion with an engineer who works for a large POE
lighting manufacturer about RFI from their equipment. I am building a new house
and doing the lighting with low voltage Ethernet cabling to LED lamps is very
attractive for cost, NEC code flexibility and easy automation. Although their
stuff is officially FCC part 15 compliant and they recommend shielded CAT6A
cables and shielded racks for the hubs and switches, the little 'pigtails"
inside the individual fixtures radiate enough that in a laboratory environment
(or doing weak signal work) he would not recommend POE lighting.
73 John N5CQ
-----Original Message-----
From: RFI <rfi-bounces+woyb10051=outlook.com@contesting.com> On Behalf Of Hare,
Ed, W1RFI via RFI
Sent: Thursday, August 24, 2023 6:35 AM
To: rfi@contesting.com; Jim Brown <jim@audiosystemsgroup.com>; AA5CT
<jwin95@yahoo.com>
Subject: Re: [RFI] LED Street lights
There is nothing incorrect in what Jim Brown said at all, and he is certainly
NOT telling people not to start near the device. He is explaining a nuance
that is important to understand to avoid a common troubleshooting error.
For the most part, on HF, devices themselves do not radiate much, but the wires
that they are connected to do. That is what Jim is explaining.
How that radiation decays with distance depends on how the noise is being
conducted onto the wiring. If the wiring were reasonably well balanced, acting
like a leaky transmission line, the strength of the noise would decay at about
60 dB/distance decade within about 0.16 wavelength from the source and/or the
source wiring. If the noise is conducted to the wiring as a common-mode
signal, the decay rate would be lower and, if the wires are long in terms of
wavelength, a standing wave along them is often developed, with peaks and
valleys that can very much confound locating the actual device source.
To understand what Jim Brown is telling you, think of an LED bulb. It is too
small to be an effective HF antenna, but those long wires it is connected to
can be great antennas. If the noise from an LED street light conducts around
(or through) the step-down transformer it is connected to and gets onto those
overhead distribution lines, it can radiate for quite a distance an in some
instances, may be stronger at some point other than right at the pole it is
attached to, depending on what antenna you are using for receive. (A loop
receive antenna may show a NULL when the null is pointed at the source, and as
you drive away, that null will disaappear.)
I have retired from HQ, but still volunteer there (quite a bit of time on this
SMC HF petition.) One of my late summer projects is going to be to set up a
moble noise-measurement system, using accurate equipment, and by late fall, I
expect to be making measurements of noise over large geographical areas.
Measuring the noise from an LED street-lighthing system in an entire community
should be quite the challenge.
From what I have seen in some of the temporary setups I have used over the
years, and from just listening on a receiver, most of the LED street lights
seem to be RF quiet. From the reports I have seen, some are not.
What I don't have is make and model number of the LED bulbs that are causing a
problem. I am sure I can persuade the ARRL Lab to buy one and we can make
measurements of its conducted emissions. That will be a good starting point.
If FCC follows its own lead on past decisions, it will proclaim those overhead
lines to be "non-residential" environments, as it did for BPL over a decade
ago, even for street lights in residential neighborhood.
Ed Hare, W1RFI, ARRL Lab Volunteer
________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of AA5CT via
RFI <rfi@contesting.com>
Sent: Wednesday, August 23, 2023 9:27 PM
To: rfi@contesting.com <rfi@contesting.com>; Jim Brown
<jim@audiosystemsgroup.com>
Subject: Re: [RFI] LED Street lights
I don't know where you're coming from Jim. How long has it been since you've
been in the 'field' with a portable SW receiver?
Noisy devices, power poles, even lighting poles all have distinctive signatures
heard when standing near them. The CLOSER you get the STRONGER will be whatever
noise/signal the device *may* be generating. Surely this aspect need not be
spelled out?
I still stand with the advice as a first tier investigation to GET NEAR THE
DEVICE and inspect the ham bands for any anomalous noise. This isn't rocket
science. This e-mail was a response to Eric for advice looking at a NEWLY
installed LED lighting pole. Eric, if you have a SW/HF radio in the car that
might be a way to do a first tier/first pass inspection of the new lighting
pole too.
de AA5CT Jim
---------------------------------
On Wednesday, August 23, 2023, 7:54:53 PM GMT-5, Jim Brown
<jim@audiosystemsgroup.com> wrote:
On 8/23/2023 5:17 PM, AA5CT via RFI wrote:
> Hmmm ... if an exotic receive apparatus is required to 'spot the noise', how
> serious could the noise really be?
Not all noise is broadband. Indeed, most electronic noise is not. And the
receiver cited makes an excellent spectrum analyzer. Most noise is radiated by
wiring, not by the fixtures themselves.
NK7Z's webpage provides lots of excellent troubleshooting advice for chasing
electronic noise.
73, Jim K9YC
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