The system I related to was at a distance of about 200-feet and detectable
out to a mile+. It was definitely not in compliance for either FCC or CE,
as claimed on the labels.
Dave - WØLEV
On Mon, Feb 5, 2018 at 5:09 PM, Hare, Ed W1RFI <w1rfi@arrl.org> wrote:
> That system would be a Class A Part-15 device, so would have to meet the
> higher industrial limits. Locally, ie near the motors, controller or
> wiring, I could well imagine a 50+ dB increase in noise from a "legal"
> device. If that were 55 dB at a nearby Amateur antenna, it is possible
> that the system exceeded the Class A limits.
>
> Ed, W1RFI
>
>
>
> -----Original Message-----
> From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of David Eckhardt
> Sent: Saturday, February 03, 2018 12:50 PM
> To: Cortland Richmond
> Cc: RFI
> Subject: Re: [RFI] RFI every 15 KHz on 160 meters, suspect source is a
> manufacturing facility.
>
> Look for AC/AC or AC/DC switching converters. I won't relate the story,
> but we had an incident where 208/3-phase was fed to several speed
> controllers on a large irrigation system (20-housepower AC motors). The
> proper and required decoupling components were not bought and installed due
> to cost. We experienced switching noises some 55 dB over baseline on a
> portable R&S spectrum analyzer. Our emissions peaked right in the middle
> of the 40-meter band but were detectable to low VHF. The controllers were
> from China with a storefront on the west coast - what else is new these
> days with no FCC enforcement.
>
> Dave - WØLEV
>
> On Sat, Feb 3, 2018 at 3:36 AM, Cortland Richmond <ka5s@earthlink.net>
> wrote:
>
> > Great Don.
> >
> >
> > On 2/2/18 8:28 PM, Don Kirk wrote:
> >
> >> Hi Cortland,
> >>
> >> Thanks for the info. I just constructed a 3" diameter loop (not
> >> tuned) using some pretty rigid RG58U, and will try it along with a 6"
> >> diameter tuned loop (adjustable between 20 and 30 MHz). I have
> >> basically tracked the RFI down to a room, but the room is packed full
> >> of motor controls (numerous VFDs, etc.). The 3" diameter loop
> >> appears to be working well with my SDR receiver based on some simple
> bench top testing I just did.
> >>
> >> Thanks,
> >> Don (wd8dsb)
> >>
> >> On Fri, Feb 2, 2018 at 4:00 PM, Cortland Richmond
> >> <ka5s@earthlink.net>
> >> wrote:
> >>
> >> Hi, gents. Cortland here, KA5S.
> >>>
> >>> I had about a 30 year career in EMC engineering, and often had to
> >>> locate specific sources of EMI.
> >>>
> >>> A quite small loop will do very well if one is in close proximity to
> >>> the magnetic field of an emitter. That is, there is a good deal of
> >>> utility in entering the near field very closely.
> >>>
> >>> You may remember the famous 3520 kHz television modems of some years
> ago.
> >>> For those I tried using three antennas; a surplus EMC loop antenna
> >>> about
> >>> 1
> >>> m in diameter, ad un-tuned whip antenna, and about a 3 inch loop
> >>> antenna made by bending a piece of semi-rigid cable back on itself
> >>> and soldering the exposed center conductor at the non-connectorized
> >>> end to the outside of the shield near the connector.
> >>>
> >>> This last was unbalanced, but its small wavelength aperture made it
> >>> good almost through VHF.
> >>>
> >>> At 80M, on a handheld receiver, it could accurately lead me to the
> >>> exact room one of those modems was radiating from.
> >>>
> >>> Much smaller loops can be constructed on the open end of a single
> >>> piece of coax, and can follow individual traces on a PWB – but that
> >>> is beyond the scope of this discussion.
> >>>
> >>> Good luck!
> >>> Cortland
> >>> ka5s
> >>>
> >>>
> >>> On 2/2/18 2:32 PM, Don Kirk wrote:
> >>>
> >>> Hi Dave and gang,
> >>>>
> >>>> I totally agree on the smaller loop, but I believe what is also
> >>>> important is to factor in the implications of being in the near
> >>>> field. That's why I think going to a much higher frequency would
> >>>> be very beneficial (get out of the near field as much as possible,
> >>>> but we will see).
> >>>>
> >>>> Stay tuned (no pun intended).
> >>>>
> >>>> Don (wd8dsb)
> >>>>
> >>>> On Fri, Feb 2, 2018 at 1:51 PM, Dave Cole (NK7Z) <dave@nk7z.net>
> wrote:
> >>>>
> >>>> I would try a a much smaller mag loop, like a foot in diameter. I
> >>>> have
> >>>>
> >>>>> used a 6 inch loop in some cases, they are still sort of directional.
> >>>>> Add a
> >>>>> ferrite on the coax at the feed point. I have one loop that is
> >>>>> about an inch in diameter, I use it seldom, but it is handy when
> >>>>> needed.
> >>>>>
> >>>>> I also have a small probe I built out of a piece of coax, I just
> >>>>> cut the shield back 3 inches, used dollop of liquid electrical
> >>>>> tape on the end of the center conductor for insulation, and then I
> >>>>> probe around...
> >>>>>
> >>>>> 73s and thanks,
> >>>>> Dave
> >>>>> NK7Z
> >>>>> http://www.nk7z.net
> >>>>>
> >>>>> On 02/02/2018 10:20 AM, Don Kirk wrote:
> >>>>>
> >>>>> Quick follow up on my locating the source of the repeating 15
> >>>>> KHz
> >>>>>
> >>>>>> signal
> >>>>>> (actually 15.6 KHz).
> >>>>>>
> >>>>>> Today I met with the suspect facilities machine controls engineer
> >>>>>> that just happens to be an inactive but still licensed ham (turns
> >>>>>> out we also have mutual friends in the machine controls world).
> >>>>>>
> >>>>>> I first walked around the entire perimeter of the building
> >>>>>> (outside in very cold temperatures) using my portable SDR system,
> >>>>>> and was able to determine that the source of the interference is
> >>>>>> located near the west central part of the building where there
> >>>>>> are several water cooling towers as well as material storage
> >>>>>> silos. The signal is indeed cyclic but still need to see how
> >>>>>> repeatable the cycle is (typically on for about 20 minutes and
> >>>>>> then off for about 20 minutes). Inside the west wall there are a
> >>>>>> bunch of facilities related equipment (pumps, variable speed
> >>>>>> drives, etc.).
> >>>>>> Unfortunately my 160 meter tuned loop is useless when in so close
> >>>>>> to the source, and we were not able to determine the actual
> >>>>>> source in the allotted time we had today. With the SDR receiver
> >>>>>> gain set at 0, the signal was still near full scale when in close
> >>>>>> to the source (it appears we have the source nailed down to about
> >>>>>> a 50 foot by 25 foot area, but there is a ton of motor controls
> >>>>>> equipment in this small area as well as metal building structure
> >>>>>> that likely is confounding our DFing).
> >>>>>>
> >>>>>> We are now going provide my vehicle description, name, etc. to
> >>>>>> the security department that patrols the grounds of this facility
> >>>>>> so they know I have permission to be on the property 24 hours a
> >>>>>> day 7 days a week. I'm going to obtain more data on the cyclic
> >>>>>> nature of the interference (to see if it provides any clues), and
> >>>>>> also evaluate capturing the signal at much higher frequencies
> >>>>>> (determine what the highest frequency is that I can still capture
> >>>>>> the signal), and then build a DF antenna for the higher frequency
> >>>>>> to help pinpoint the source when in close. After I obtain more
> >>>>>> data from outside the building and develop a better antenna for
> >>>>>> in close DFing, I will then go back into the building to continue
> >>>>>> our in close DFing (as time permits).
> >>>>>>
> >>>>>> My portable SDR system consists of a Dell laptop, NooElec SDR
> >>>>>> dongle, and ham it up converter (stuck to the back of the laptop
> >>>>>> screen using double stick tape). The SDR dongle and ham it up
> >>>>>> converter are powered via the laptop USB ports which makes it
> >>>>>> very convenient. I just plug my DF antenna into the ham it up
> >>>>>> converter and adjust the SDR dongle gain as needed (via the
> >>>>>> SDRSharp software I'm using).
> >>>>>>
> >>>>>> Just FYI,
> >>>>>> Don (wd8dsb)
> >>>>>>
> >>>>>> On Mon, Jan 22, 2018 at 9:15 AM, Don Kirk <wd8dsb@gmail.com> wrote:
> >>>>>>
> >>>>>> Yesterday I tracked down RFI that has been bothering me on 160
> >>>>>> meters for
> >>>>>>
> >>>>>> the past year. The source was a little hard to find because it's
> >>>>>> not
> >>>>>>> always on. I finally had to use my SDR dongle with Ham it up
> >>>>>>> converter in the car with my small tuned loop to track down the
> >>>>>>> source of the interference (in order to make sure what I was
> >>>>>>> seeing at home was what I was actually tracking). The suspect
> >>>>>>> source is 0.75 miles from my house.
> >>>>>>> Here is a link to a video showing my efforts to date.
> >>>>>>>
> >>>>>>> http://www.youtube.com/watch?v=LKf1EWTV8xs
> >>>>>>>
> >>>>>>> Today I will contact the manufacturing facility that I tracked
> >>>>>>> the RFI down to in order to take the next step with them.
> >>>>>>>
> >>>>>>> I will report the actual source of the RFI as soon as it's
> >>>>>>> determined which might take some time (usually takes time to
> >>>>>>> establish a good working relationship with the suspect property
> >>>>>>> owner). Based on past experience it sure looks like a variable
> >>>>>>> speed drive, but in order to keep an open mind I try not to
> >>>>>>> guess ahead of time.
> >>>>>>>
> >>>>>>> Just FYI,
> >>>>>>> Don (wd8dsb)
> >>>>>>>
> >>>>>>> _______________________________________________
> >>>>>>>
> >>>>>>> RFI mailing list
> >>>>>> RFI@contesting.com
> >>>>>> http://lists.contesting.com/mailman/listinfo/rfi
> >>>>>>
> >>>>>> _______________________________________________
> >>>>>>
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> >>>>> _______________________________________________
> >>>>>
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> >>>>
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>
>
> --
>
> *Dave - WØLEV*
> *Just Let Darwin Work*
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--
*Dave - WØLEV*
*Just Let Darwin Work*
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