[RFI] Powerline noise question

Dave (NK7Z) dave at nk7z.net
Fri Dec 30 21:12:24 EST 2022


Hi Scott,

I programmed up 30 or 40 memories, (following someone's suggestion 
here), starting at .5 MHz, and ending at 450 MHz, in almost equal steps, 
all AM.  I just go into memory mode, look at the RFI both on the 
waterfall, and on the O-Scope, dip the offending source if possible, and 
move up in frequency by turning a single knob to the highest frequency I 
hear the RFI at.  I then move to a new spot and do it again...  I also 
use a program on my iPhone called SigTrax.  (see: 
https://apps.apple.com/us/app/sigtrax/id714920367), I have attached two 
of the resultant run results.

I also use the O-Scope in the IC-705, in addition to the waterfall... 
As you said, all in one package...  It for my money, is the best RFI 
hunting setup I can afford right now...  I would love one of the RADAR 
units, but alas, cost is an issue for that device...

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 13:17, nm8rmedic wrote:
> Don't overlook the audio waveform 'oscilloscope' functionality of the 
> IC705 as a means of identifying 60 and 120 Hz components of an arcing 
> source.  It's all there, in one easily portable package.
> 
> I second NK7Z's use of the '705.  Mine in combination with a National 
> HFDF loop system made it easy to track down the 6 M Wireless headset 
> interference I was experiencing.  Ed and Steve of the ARRL were very 
> helpful in that endeavor.
> 
> Scott
> NM8R
> 
> 
> 
> Sent from my Verizon, Samsung Galaxy smartphone
> 
> 
> -------- Original message --------
> From: "Dave (NK7Z)" <dave at nk7z.net>
> Date: 12/30/22 13:39 (GMT-05:00)
> To: "Hare, Ed, W1RFI" <w1rfi at arrl.org>, rfi at contesting.com
> Subject: Re: [RFI] Powerline noise question
> 
> 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:
>  >>
>  >>>
>  >> _______________________________________________
>  >> RFI mailing list
>  >> RFI at contesting.com
>  >> http://lists.contesting.com/mailman/listinfo/rfi
>  > <http://lists.contesting.com/mailman/listinfo/rfi>
>  > _______________________________________________
>  > RFI mailing list
>  > RFI at contesting.com
>  > http://lists.contesting.com/mailman/listinfo/rfi
>  > <http://lists.contesting.com/mailman/listinfo/rfi>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi


More information about the RFI mailing list