[RFI] Xfinity Router RFI (Xfinity router name XB3)

Jim Brown jim at audiosystemsgroup.com
Thu Feb 13 12:37:00 EST 2020


This is a very interesting post, Don.

Your loop and a description of your troubleshooting would make a great 
piece for QST or NCJ. Also, spectrum pix would make a great addition to 
NK7Z's collection of the signatures of known noise sources.

For chokes wound on the 2.4-in o.d. #31 cores, I suggest following 
recommendations for THHN for cables like AC line cord and RG400 for 
smaller cables in the New Cookbook.

73, Jim K9YC

On 2/13/2020 6:59 AM, Don Kirk wrote:
> Hi Jim (and gang),
> 
> I should also mention the wireless router we are talking about is really 
> called a Residential Gateway.
> 
> The Xfinity Telephony Gateway provides four Ethernet connections for use 
> as thehub of your home/office Local Area Network (LAN). The Xfinity 
> Telephony Gatewayalso provides 802.11a/b/g/n/ac wireless connectivity 
> for enhanced mobility andversatility. In addition, the Xfinity Telephony 
> Gateway provides for up to two sepa-rate lines of telephone service and 
> Digital Enhanced Cordless Telecommunications(DECT) funtionality to allow 
> using cordless telphones within the home. The Tele-phony Gateway also 
> offers integrated MoCA 2.0 home networking providing Inter-net access 
> and transfer of multimedia content between devices over coaxial cablein 
> the home.
> 
> Just FYI,
> Don (wd8dsb)
> 
> On Thu, Feb 13, 2020 at 9:40 AM Don Kirk <wd8dsb at gmail.com 
> <mailto:wd8dsb at gmail.com>> wrote:
> 
>     Hi Jim,
> 
>     Thanks, but I really wanted to know if others have noticed a 1 MHZ
>     wide signal that has a white noise waterfall and spectrum plot (both
>     RF and Audio) from the Wireless Router I mentioned centered around
>     21 MHz.  The main reason I asked this question is that it took us a
>     couple of days to track down the source because at times we had
>     conflicting bearings from our numerous direction finding antennas
>     and I now suspect we ran across similar signals originating from
>     other homes in a pretty densely populated neighborhood.
> 
>     This case made me introduce a new portable direction finding antenna
>     to my toolkit for HF which turned out to be a life saver.  I have a
>     lot of experience with small terminated flags and pennants on 160
>     meters, and this gave me the idea to design and build a very small
>     portable terminated flag that I designed to have a cardioid pattern
>     all the way up to at least 30 MHz, and this antenna was a great help
>     due to its unidirectional properties.  Used this portable flag (2
>     foot x 4 foot) with a W7IUV preamp operating off a 9 volt battery
>     and this system was invaluable.  A big advantage of the terminated
>     flag is that it's truly broadband versus the portable tuned loops we
>     also used.  Having the broadband antenna allowed us to easily see
>     the 1 MHz signature of the signal. (where it rolled off, etc.).
> 
>     Please keep in mind that when we are dealing with a homeowner that’s
>     also a stranger that’s not a ham we should try and be the least
>     invasive and least time consuming as possible while still obtaining
>     the end goal which is to eliminate the RFI we are experiencing.  We
>     got lucky that this particular homeowner immediately volunteered to
>     shut off his breakers before we even asked him to do that until we
>     found what circuit was generating the noise, and then he went into
>     his master bedroom and started unplugging devices until the device
>     generating the noise was located (Mike and I did not enter his
>     home).  He then mentioned he was going to go to xfinity on Monday
>     anyway and would request a new wireless router.  It also helped that
>     this homeowner had some knowledge of who Mike was and he mentioned
>     that he had gone to high school with Mikes son many years ago.
> 
>     As I already mentioned we indeed will have the home owner try a
>     toroid choke (based on the 31 material) on his AC line cord as well
>     as a traditional differential mode power line filter if new
>     equipment from Xfinity does not solve the problem.  If these methods
>     don’t work then we will dig deeper (chokes on other cables entering
>     and exiting the wireless router, etc.).
> 
>     On a side note, Mike (W9RE) is going to give the homeowner an
>     extension cord wrapped on our 31 material toroid core to try on his
>     existing router prior to this weekend since Mike as I'm sure you
>     know is big contester and he sure would like to have his 15 meter
>     noise reduced (or eliminated) for this weekends contest, but again
>     we are not trying to be too over bearing on this homeowner since he
>     has already been so cooperative.
> 
>     Will post an update in the near future.
> 
>     Thanks and 73,
>     Don (wd8dsb)
> 
> 
> 
> 
>     On Wed, Feb 12, 2020 at 9:39 PM Jim Brown <jim at audiosystemsgroup.com
>     <mailto:jim at audiosystemsgroup.com>> wrote:
> 
>         On 2/12/2020 6:18 PM, Don Kirk wrote:
>          > If the replacement router does not fix the problem then
>          > Mike will test a toroid core choke as well as a corcom type
>         filter on the
>          > wireless router power cord.
> 
>         It's ALWAYS a good idea to put a suitable ferrite choke on any
>         wiring
>         connected to a noise source -- it's usually those wires that
>         radiate the
>         noise. And that includes the AC line cord or DC power cable. For
>         15M,
>         I'd start with three turns on a medium-size #31 clamp-on, and
>         I'd do the
>         same with any Ethernet cables.
> 
>         If you haven't already done so, I'd try to shift the network to
>         WiFi, so
>         that the only cables are the power supplies, the cable between
>         the modem
>         and the router, and the DSL or internet cable feeding the modem.
> 
>         Lots of detailed advice on my website in the piece about increasing
>         contest scores by killing noise. k9yc.com/publish.htm
>         <http://k9yc.com/publish.htm>
> 
>         73, Jim K9YC
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