[RFI] 160 meter noise at W9RE tracked down to neighbors Comcast Cable Box / Power Supply
Dave Cole
dave at nk7z.net
Sun Feb 23 12:37:52 EST 2020
Thanks Jim, nice video... I'll send you a private note so we don't
hijack the 160/Comcast thread any further...
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 9:04 AM, AA5CT wrote:
>
> re: "I need to move to the country, with a hill between me and all cities, or ..."
>
> Or, look at what Horizontal Waller Flag can do. N4IS Jose Carlos has a good YT
> video on what the transmit antenna, then the Waller Flag V and H does to 'noise'
> and allowing the signal to "shine through".
>
> 73, de AA5CT Jim
>
> .
> .
>
>
> On Sunday, February 23, 2020, 9:50:10 AM GMT-6, Dave Cole <dave at nk7z.net> wrote:
>
>
>
>
>
> Here is an interesting datum regarding RFI...
>
> I have a friend that lives two miles from me, I live in the city, he
> lives in the country, with a large rock hill between him and the same
> city I live in...
>
> Last night I was listening to VP8PJ on 40 CW, I could almost hear him
> with my 6BTV, and 40 radials on the ground. I would pick out a 5NN now
> and then.
>
> Using his rig, over the phone, he was hearing VP8PJ at 100% in the
> clear... Copyable 100% across a crappy phone line... For me, this was
> the quiet time for RFI, S4 to S5. His background RFI on 40, S1...
> VP8PJ was S3 at his place.
>
> Both of us have the same rig, same antenna, same number of radials... I
> need to move to the country, with a hill between me and all cities, or
> get a remote receiver.
>
> 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 7:36 AM, Don Kirk wrote:
>> 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
>> <mailto: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 <mailto: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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