[RFI] 160 meter noise at W9RE tracked down to neighbors Comcast Cable Box / Power Supply

[Don Kirk]

Hi Dave,

I totally agree with your statements and similar to how I use my SDR gear.

Thanks,
Don

On Sun, Feb 23, 2020 at 10:10 AM Dave Cole <dave at nk7z.net> wrote:

> Hi Don,
>
> I tend to agree with you somewhat on the SDR issue-- SDR is great at
> defining what noise type one is having, what your general RFI
> environment looks like, and in general, what is happening around you in
> the RFI world.
>
> However it will not in most cases, let you say, "Oh, look there is a GE
> oven clock on a GE model 12345".
>
> SDR will let you say, I have some very broadband RFI, or I have some
> narrow band RFI, the the RFI I have is on a schedule,etc., and that type
> of data, tends to point to these types of devices, etc.
>
> SDR helps define the tools needed to hunt, and some indications as to
> what you might be looking for...  SDR will help you define when to hunt,
> if your source is on a schedule, etc...
>
> So in the way of "lets ID the source to the part number", sort of way, I
> agree, we are slipping a bit into that mode using a SDRs.
>
> I use my SDR to point me in a general direction for tools, hunting
> methods, and times...
>
> I also use it to quantify what my RFI is prior to a fix, and then check
> after the fix.  SDR has its place, but it is not defining an RFI source
> to the item part number.
>
> Every 6 months to a year, I do a full spectrum record of my RFI across a
> 24 hour period using HDSDR, then save that data.  That helps me see what
> is happening around me over time...  There is a place for SDR in RFI
> hunting-- as a guide to what further steps to take, and in defining what
> is happening around you over long time frames...
>
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist
> ARRL Asst. Director, NW Division, Technical Resources
>
> On 2/23/20 5:12 AM, Don Kirk wrote:
> > Hi Jim,
> >
> > Thanks.
> >
> > I know and follow your guidelines really well, but I have to tell you
> that
> > when working in someones house that is not a hams we should not be
> > installing anything special if at all possible (unless it's indeed one
> > simple choke on the power cord and that's even pushing it).  We should
> > first hold the company that installed or supplied the hardware
> responsible
> > for a clean solution.  In this case if it's the switch mode power supply,
> > then Comcast can easily provide them a different power supply or a
> > different Cable box that uses a different power supply to see if that
> fixes
> > the problem.  The homeowner is actually going to take his Comcast cable
> box
> > and power supply to Comcast on Monday and ask for some different
> hardware.
> > We also showed the homeowner how they can easily test possible solutions
> > using their AM radio if Comcast technicians come to their house as right
> > now they can't hear any AM radio stations unless they unplug their
> Comcast
> > cable box power supply.  They will also be working with Mike for possible
> > solutions, but as I said we should try and find the correct solution if
> > possible versus installing our band aids all over the place in a
> strangers
> > home.  We are lucky in this case that the homeowners are very open and
> > willing to go the extra mile to help Mike (W9RE), so if commercial
> > solutions do not work then Mike can indeed take the band aid approach but
> > again I prefer to go the commercial route solution if at all possible.
> >
> > We did try a choke made per your guidelines on the power cord, and it had
> > no effect.  I often try your choke on power cords, and sometimes they do
> a
> > fantastic job, and other times not (sometimes probably due to issues like
> > you mention about other cables entering and exiting the box, but
> sometimes
> > it was due to the fact that I needed to use a differential mode filter on
> > the power line or a combination of both).
> >
> > While I'm preaching, I also think we have gotten overboard on this
> > reflector regarding SDR screen shots, audio recordings of noise, etc.
> from
> > people asking what their source of RFI might be.  Time and time again
> while
> > out tracking down noise I have found that the only thing that matters is
> to
> > identify the property (location) generating the noise using radio
> direction
> > finding equipment (which can often be very simple home brew equipment
> which
> > most of mine is), and then track down the offending device within the
> > property.  Too many times when I'm out hunting down noise that's
> bothering
> > another ham we waste time and take too many tangents when one thinks they
> > know what the source is.
> >
> > Just my opinion, and a little cranky after tracking down too many noise
> > sources this week and it's just a hobby, and I still have a day job with
> > lots of worldwide travel.  On the positive side I sure got a lot of steps
> > in on my Fitbit this week.
> >
> > 73,
> > Don (wd8dsb)
> >
> >
> >
> >
> >
> > On Sun, Feb 23, 2020 at 3:42 AM Jim Brown <jim at audiosystemsgroup.com>
> wrote:
> >
> >> On 2/23/2020 12:22 AM, Don Kirk wrote:
> >>> They are now going to work with Comcast and Mike to find a solution as
> a
> >>> power line choke made with a number 31 material Toroid core did not
> >> reduce
> >>> the RFI.
> >>
> >> Don (and Mike),
> >>
> >> Every cable connected to the box can be an antenna so it needs a choke.
> >> I'd start with the coax and power. Use the guidelines in the chasing
> >> noise app note below and the new HF choke cookbook, depending on the
> >> size of the cable you're choking and the frequency(ies) that are
> >> bothering you. See Fig 2 on page 2 and the associated discussion.
> >>
> >> http://k9yc.com/KillingReceiveNoise.pdf
> >>
> >> 73, Jim K9YC
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