[RFI] Powerline noise question

[Dave (NK7Z)]

I use the waterfall only for pattern recognition for DFing...  I gave up 
long ago trying to define what is causing RFI!  :)

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 12/30/22 09:58, Hare, Ed, W1RFI wrote:
> The SDR waterfall will not be very helpful with power-line noise, but 
> they are great at identifying switching power supply noises and noises 
> that pulse on and off in a regular pattern.
> 
> Most of the time, though, we are less concerned with "what is it" as we 
> are with "where is it?"
> 
> ------------------------------------------------------------------------
> *From:* RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of 
> Dave (NK7Z) <dave at nk7z.net>
> *Sent:* Friday, December 30, 2022 12:08 PM
> *To:* rfi at contesting.com <rfi at contesting.com>
> *Subject:* Re: [RFI] Powerline noise question
> Something else that might help you differentiate one source from another
> source in the pile of other signals-- a portable SDR.
> 
> I now use an Icom IC-705 as my goto RFI hunt tool when mobile...  Self
> contained for power, and it has a waterfall!
> 
> The waterfall makes it a simple matter to ID one source, (most of the
> time), then as you rotate your flag, or loop, you see only that source
> dip...  You know you have the right signal, and can DF only that one...
> 
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net <https://www.nk7z.net>
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
> 
> On 12/29/22 20:07, Don Kirk wrote:
>> Hi Rick,
>> 
>> Sorry that my last message was blank as I typed it on my cell phone and
>> then accidentally deleted the text prior to hitting the send key.
>> 
>> You can use your MF/HF loop to do some triangulation on the source but you
>> often need to get far away from existing power lines to avoid receiving
>> conducted signals along the lines versus the signal direct from the
>> source.  As an example when out in the country I will often walk out into
>> the middle of farm fields to get away from overhead power lines when
>> obtaining bearings.  As you get closer to the source you can go higher in
>> frequency if it really is power line noise (arcing hardware).  As an
>> example you can go to 40 meters then 20 meters and then 10 meters as you
>> get closer to the source as a form of attenuation and to also help you get
>> multiple wavelengths away from objects that might otherwise skew your
>> readings.  Adjustable RF gain and/or attenuators are also very helpful.
>> 
>> If it really is power line noise (arcing hardware) you should be able to
>> hear the source using an AM receiver with a 3 or 4 element yagi when you
>> are within approximately 0.25 miles of the source (and sometimes upto 0.5
>> or more miles away).  Make sure the yagi is tuned for the frequency you are
>> using in order to assure the correct antenna pattern.  When you get very
>> close to the suspect pole you will typically need to throw in 20 to 30 dB
>> of attenuation in order to determine the exact pole (in rare cases you
>> might even need 40 dB of attenuation).
>> 
>> One thing that is great is that it sounds like your source has a specific
>> pattern that will help you differentiate it from other sources but if the
>> pattern is always a very specific 0.9 second pattern that never changes
>> regardless of what day you listen, etc. that makes you wonder if something
>> else is going on, but the fact that it goes away when it rains is typically
>> a good indicator that it's indeed power line noise (arcing hardware).
>> 
>> Don (wd8dsb)
>> 
>> On Thu, Dec 29, 2022 at 10:46 PM Don Kirk <wd8dsb at gmail.com> wrote:
>> 
>>>
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