Hi Jim
Thanks, and I thought about submitting an article to QST since I have
written articles for them in the past, and will do that for my portable
flag for HF direction finding. Numerous people have requested info from me
already today, and will put something together soon and provide a link to a
simple website (probably sometime next week).
I had been working on a tuned loop with sense antenna but then thought
about designing the portable flag and glad I did as it really keeps things
simple and easy to duplicate (very robust concept and hard to mess up).
Just came in from the cold testing its directional properties from the AM
broadcast band all the way up to 25 MHz (max frequency of the signal
generator I was using today), but as I previously said I designed it using
4NEC2 so it has a cardioid pattern up to at least 30 MHz and actually
higher in frequency. It has very negative gain (especially down on 160
meters) but works great when using an appropriate preamp. In most cases a
20 dB preamp like the W7IUV preamp is more than adequate but in some cases
even more preamp might be helpful.
Lots more info to follow, but since I have a day job it will take some time
to put together my article for submission to QST but I should be able to
post some pictures, dimensions and other design info sometime next week on
a simple website I will create for this antenna.
73,
Don (wd8dsb)
On Thu, Feb 13, 2020 at 12:37 PM Jim Brown <jim@audiosystemsgroup.com>
wrote:
> 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
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com <mailto:RFI@contesting.com>
> > http://lists.contesting.com/mailman/listinfo/rfi
> >
>
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