Don,
A decade or more back I built a 10m dipole for use up on the roof to find a
noise in the neighborhood. Maybe it was two decades back! And it worked
well for getting a bearing to go out searching on ... turned out to be the
house across the street - a ceiling fan -that was turned on in the morning
and off in the evening! Loose connection in the junction box was making
arcing noise at a cyclic rate as the fan rotated!
Good luck in finding that signal on 21 MHz. My 'white whale' was a fast
drifting voice-modulated signal on 440 MHz that could not be heard while
using a hand-held beam on the roof - only the high-gain station antenna
at 40 ft would catch it!
Finally, years later, I was able to correlate it with a commercial radio 2-way
service that was really weak here ... turned out to be Dallas Water Utilities!
They migrated to a new radio system shortly thereafter ...
73, de AA5CT Jim
On Sunday, February 23, 2020, 11:44:05 AM GMT-6, Don Kirk <wd8dsb@gmail.com>
wrote:
Hi Jim,
Interesting that you mention V and H.
There is an elusive signal W9RE and I have been chasing on 21MHz and just this
morning I told Mike that we might considering looking at the signal using
horizontal orientation of my portable flag versus vertical that we have been
using since his 21 MHz beam that’s horizontal hears the signal and a lot of
houses real close to him appear to be masking the signal we are looking for
when we are at ground level versus 150 or 200 feet up in the air where his 21
MHz beam is located. We have identified numerous signals from his various
neighbors houses using vertical orientation but not necessarily the one he sees
with his horizontal beam way up in the air.
Just FYI,
Don (wd8dsb)
On Sun, Feb 23, 2020 at 12:04 PM AA5CT <jwin95@yahoo.com> 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@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@nk7z.net
>> <mailto:dave@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@audiosystemsgroup.com <mailto:jim@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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