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> 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
>
> 73, Jim K9YC
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|