[RFI] New RFI

[K9MA]

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?
>>>>

-- 
Scott  K9MA

k9ma at sdellington.us