[RFI] Help finding a source

Thu Dec 5 10:58:42 EST 2019

FWIW, I built a 136-MHz Moxon from a QST article <QST_Mar_2001_p32-36> 
to use with an Icom handi-talkie which covers the AM aircraft band. The 
idea is that the Moxon has a deep dip in the rear which can be used for 
precise DFing.   Works fine, and I got 144/430 MHz transceive coverage 
as a bonus ( though not with that antenna) for around $100.

73, Pete N4ZR
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On 12/5/2019 8:20 AM, Michael Martin wrote:
> The mfj with the beam is probably the cheapest most convenient and best little RFI locator I've ever come across. I bought one back when they first came out and decided to do a little modifying. I added an amplifier between the radio in the antenna and an attenuator and then an external speaker. It was quite a good locator. The beam is quite fragile but for someone who just needs to find one noise every now and then I think this is about as good as you can get.
>
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> On Dec 5, 2019, 4:52 AM, at 4:52 AM, Bill Steffey <ny9h at arrl.net> wrote:
>> Hi,
>>
>> mfj still sells a #852   which is nothing more than a VHF am receiver
>> with a dipole integrated onto the case.. ..  Bought one new 14 years
>> ago
>>    then found another at a hamfest for 40$ .
>>
>> After showing Commonwealth Edison rfi guy my panadapter and the beam
>> heading stuff, I took him into the neighbors back yard with this little
>>
>> box with a meter & headphones. Straight to the bad pole. He said it
>> worked better than the Radar Engineers equipment ...( not quite)
>> ....and
>> at that price his boss could get a few MFJs rather than passing around
>> the expensive boxes... at least till need was indicated.  For powerline
>>
>> noise it is nothing but an aircraft AM receiver with a dipole ...which
>> you retract for attenuation as you approach the suspect.  WORKS
>> GREAT....   They sell the same meter with a beam for more money,,,
>>
>> https://www.mfjenterprises.com/Product.php?productid=MFJ-852
>>
>>
>>
>> On 12/5/2019 4:24 AM, Don Kirk wrote:
>>> Hi Michael,
>>>
>>> You mentioned three discharges per half cycle, but looks like it
>> would be
>>> three discharges every other half cycle (if it is indeed power line
>>> equipment) since the period between the groups of 3 is around 16.7ms,
>> not
>>> 8.3 ms.
>>>
>>> Don (wd8dsb)
>>>
>>> On Wed, Dec 4, 2019 at 7:19 PM Michael Martin <mike at rfiservices.com>
>> wrote:
>>>> your noise is caused by loose hardware on the power line equipment.
>>>> the three spikes you see per group represent three discharges per
>> half
>>>> cycle
>>>>
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>>>>
>>>> On Dec 4, 2019, 5:07 PM, at 5:07 PM, David Eckhardt
>> <davearea51a at gmail.com>
>>>> wrote:
>>>>> I give up.        It's power line discharge.
>>>>> Dave - WØLEV
>>>>>
>>>>> On Wed, Dec 4, 2019 at 11:24 PM Michael Morgan <michael at aa5sh.com>
>>>>> wrote:
>>>>>
>>>>>> I was hoping to get some help identifying a potential source for
>> some
>>>>> RFI
>>>>>> that started a few weeks ago.  I posted some pictures and audio
>> clips
>>>>> from
>>>>>> 20 and 40 meters on my webpage.  Thought it may be easiest there I
>>>>> hope it
>>>>>> is ok.  https://www.aa5sh.com/?p=328
>>>>>>
>>>>>> I tried to get some screenshots from my 7610.  On 20M the Noise
>>>>> Blanker
>>>>>> does  a decent job of removing the noise but on 40M it is a bit
>> two
>>>>> random.
>>>>>> I have tried turning the main breaker off to my house and use a
>>>>> portable
>>>>>> radio (Recent RS-918) off a battery and the noise is still there.
>> I
>>>>> did
>>>>>> walk around my property and noticed no real differences.  The odd
>>>>> thing is
>>>>>> it's kind of random.  It has been going to 30 Mins or so and it
>> just
>>>>>> stopped for a minute while I've been typing this email for a
>> minute
>>>>> or so
>>>>>> then started back up.
>>>>>>
>>>>>> Then at lunch today I took a break and remoted home since I saw
>> where
>>>>> 10M
>>>>>> was open and there was no noise for that 30-40 minutes.
>>>>>>
>>>>>> I appreciate any guidance you can provide.  In my years of radio
>>>>> anytime I
>>>>>> have had noise problems I have always been able to narrow it down
>> to
>>>>>> wall-wart or battery charger.
>>>>>>
>>>>>> 73
>>>>>>
>>>>>> Michael, AA5SH
>>>>>> _______________________________________________
>>>>>> RFI mailing list
>>>>>> RFI at contesting.com
>>>>>> http://lists.contesting.com/mailman/listinfo/rfi
>>>>>>
>>>>> One very last try:  Copy to Word.  Eliminate image.  Copy test with
>> no
>>>>> image.  Paste to email.  If this doesn't work, I give up:
>>>>>
>>>>> In your third image, the audio spectrum, the groups (first peak of
>>>>> first
>>>>> group to first peak of next group) is 17.5 ms.
>>>>>
>>>>>
>>>>>
>>>>> The period on one cycle at 60 Hz is 16.67 ms.  Very close.  The
>> sound
>>>>> clip
>>>>> also sounds suspiciously like 60 Hz discharge from the power
>>>>> distribution
>>>>> somewhere in your vicinity.  I usually detect this at 120 Hz as the
>>>>> discharge occurs at both the + and - peaks of the sine wave.  But
>> not
>>>>> in
>>>>> this case.  In the time domain, I also usually detect an
>> exponentially
>>>>> decaying envelope for each discharge.  No so in this case.  But,
>>>>> considering the period and sound, I'd guess its due to power
>>>>> distribution
>>>>> discharge in you area.  Walk the power lines with your
>> battery-powered
>>>>> radio.  When you find a pole that is particularly, kick the pole
>> hard
>>>>> and
>>>>> observe any change in the character of the sound on your radio.  If
>> no
>>>>> change, its not at that pole.  Continue searching.  Also, damp
>> weather
>>>>> usually exacerbates the discharges as does dusty conditions.
>>>>>
>>>>>
>>>>>
>>>>> Dave - WØLEV
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> *Dave - WØLEV*
>>>>> *Just Let Darwin Work*
>>>>> *Just Think*
>>>>> _______________________________________________
>>>>> RFI mailing list
>>>>> RFI at contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/rfi
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