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@gmail.com
<mailto:wd8dsb@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@audiosystemsgroup.com
<mailto:jim@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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