[RFI] New RFI

[Joe]

I have used all sorts of direction finding stuff. From 2 meters Fox hunt 
stuff, to the 138~ Mhz AM yagi and scanner.

BUT what I still find to be the absolute best is the simplest, And if 
you don't already have one, you probably can get one for like 5 bucks! 
The simple old portable AM reciever. You know the 550 to 1700 Khz 
Broadcast band,. The old farts would say the Transistor Radio.

That ferrite bar antenna has nulls off the end that are like infinite 
deep. and extremely narrow. I'd wager the nulls 3 db points are only a 
degree or two wide.  Lets see you get that kind of accuracy with a 4 
element beam on 2 meters.

I was helping a local try to find a noise on his farm that was totally 
killing his HF, 20+ db over most times. He has tried the as described 
above (not the AM radio I think he thought I was full of something you 
find a lot of on a farm when i suggested the AM Radio)

He just could NOT find the source. He did not even think it was on HIS 
farm.  I drove my car first listening to an empty spot on the AM radio 
and when I started hearing the noise I got out and used the little 
radio, got a beam heading, or should I say NULL heading, I was probably 
almost a mile from his house it's that bad!

drove 1/2 way towards his place took a nother reading and drew it on the 
map. well I see where they are crossing

I do it a few more times even past his place and it all points to his place.

I park in his driveway get a null and walk in it's direction. it's LOUD!

But in less than 5 minutes I'm standing next to a silo, and a wire that 
is going underground somewhere. the Null is incredible when I am even 
only inches away from that wire if it is off the ends of that ferrite 
bar there is no noise but move 1/2 a inch away from that wire in a side 
to side sweep and BOOM BBBZZZZZZZZZZZZZ.

It is incredible the accuracy!

Joe WB9SBD

On 1/13/2021 12:11 AM, K9MA wrote:
> I haven't tried using an antenna with a sharp null, but I wonder how 
> well it really works with power line noise. The problem seems to be 
> that the lines themselves radiate so much that it often appears that 
> the noise is coming from some distance away from the true source. What 
> sort of experience have others had?
>
> I like the idea of the 135 MHz Moxon, though. It would be a lot 
> smaller than the yagi on the MFJ-856, too.
>
> 73,
> Scott K9MA
>
> On 1/12/2021 3:25 PM, N4ZR wrote:
>> Using a Moxon antenna is another way to get a sharper null - there 
>> was an article in QST describing such an antenna, which I use with a 
>> shirt-pocket handi-talkie with 136 MHz AM aircraft band.  The null 
>> off the back is deep and narrow.
>>
>> 73, Pete N4ZR
>> Check out the new Reverse Beacon Network
>> web server at <http://beta.reversebeacon.net>.
>> For spots, please use your favorite
>> "retail" DX cluster.
>>
>> On 1/12/2021 1:41 PM, David Eckhardt wrote:
>>> Most recently, I have isolated a source on a power pole by using 
>>> both the
>>> MFJ device AND a home brew 0.5-meter shielded loop connected to a
>>> battery-powered receiver tuned to the frequency of maximum RFI. The 
>>> null
>>> perpendicular to the loop plane is extremely sharp and, from that
>>> experience, I dare say sharper than the MFJ device or at least an 
>>> equal.
>>> Another strength of the shielded loop is that you can isolate the 
>>> source
>>> *at* the interfering frequency(ies).   Also, confirming a source 
>>> with two
>>> entirely different technologies can be helpful in nailing the source.
>>> Once isolated, our power provider, PVREA (N. Colorado), had the problem
>>> fixed the next day and waited for us to confirm their fix. Not all
>>> providers are so responsive.
>>>
>>> Dave - WØLEV
>>>
>>> On Tue, Jan 12, 2021 at 1:25 PM Dave Cole <dave at nk7z.net> wrote:
>>>
>>>> Hello,
>>>>
>>>> I have some RFI location information at:
>>>>
>>>> https://www.nk7z.net/i-have-rfi-now-what-locating-it/
>>>>
>>>> I use the MFJ-856, (https://mfjenterprises.com/products/mfj-856), when
>>>> looking for VHF RFI.  It will pinpoint an RFI source and in most cases
>>>> you can tell which part of the house the RFI is coming from, if you 
>>>> are
>>>> on the sidewalk in front of the home.
>>>>
>>>> Your RFI could be anything, is it on a schedule, does it change
>>>> strength, lots of questions to answer first.
>>>>
>>>> IDing via signature can sometimes work, (not too often), but 
>>>> nothing has
>>>> worked for me better than getting out on foot and looking for the RFI
>>>> source.
>>>>
>>>> Once you have it located that is another entirely different matter.
>>>>
>>>> 73, and thanks,
>>>> Dave (NK7Z)
>>>> https://www.nk7z.net
>>>> ARRL Volunteer Examiner
>>>> ARRL Technical Specialist, RFI
>>>> ARRL Asst. Director, NW Division, Technical Resources
>>>>
>>>> On 1/11/21 8:45 PM, RALPH GRANCHELLI wrote:
>>>>> Hello inteference investigators,
>>>>>
>>>>> I have new RFI issue that started about a week ago.
>>>>>
>>>>> I have eliminated the house /  items as a source.
>>>>>
>>>>> Killed all breakers, ran the XCRV from batt. No change. 
>>>>> Disconnected ext
>>>>> antenna, used in house antenna and no noise. So noise coming in 
>>>>> from ext
>>>>> antenna.
>>>>>
>>>>> The RFI is strongest on 80 meters however it is present up to vhf 
>>>>> with
>>>>> diminished magnitude.
>>>>>
>>>>> I took a screen shot of it on the spectrum scope.
>>>>>
>>>>> Does anyone recognize the signature?
>>>>>
>