[RFI] Difficult power line RFI find.

[K9MA]

If your local utility is cooperative, they may share with you maps of 
their distribution lines.

73,
Scott K9MA


On 3/10/2021 11:18 AM, Don Kirk wrote:
> Hi Eddie,
>
> Thanks for sharing your very similar story, and very interesting based on
> the configuration of lines I was dealing with.  As a matter of fact I was
> using Google Earth this morning to look at the lines I was dealing with
> yesterday and wish I knew more about power distribution to better
> understand all the hardware.  Nevertheless I too was dealing with parallel
> running lines  in the area where I found the suspect pole.  One set of
> lines which appear to be 3 phase run the full length of the road on the
> North side of the street, and the suspect pole I located was also on the
> North side of the street but it was fed by parallel running lines on the
> South side of the street and I don't believe the South side of the street
> lines are 3 phase.  The suspect pole then fed some additional poles running
> up a very long driveway to a house set way back off the road.  The lines
> that my antennas always pointed perpendicular to were the 3 phase lines on
> the North side of the street which were not physically connected to the
> lines with the suspect pole as far as I can tell, and if my theory is
> correct that would say the RFI I was getting induced into the 3 phase lines
> by the lines running on the South side of the street that were connected to
> my suspect pole.
>
> We shall see, but boy my story sounds very familiar with yours as far as
> parallel running lines with a cross over to my suspect pole right under
> what I'm calling the 3 phase lines that run the full length of the street
> East/West.
>
> Thanks,
> Don (wd8dsb)
>
> On Wed, Mar 10, 2021 at 10:49 AM EDWARDS, EDDIE J <eedwards at oppd.com> wrote:
>
>> Don,
>>
>> Great story!  Thanks for sharing.
>>
>> We had a very similar experience near my QTH several years ago affecting
>> my home location and also another ham on about a mile north of me.  Only
>> difference was it was strong on low bands, and it was strongest on 80
>> meters at S9+, and probably on 160meters too but neither of us had antennas
>> for 160 meter back then.  The other ham is a mile north of me and we are
>> both in nearly a north-south line perpendicular to a 161 KV transmission
>> line.
>>
>> Also, I should mention that I work in the utility department that is
>> responsible for tracking power-line noise although it's our technicians
>> that do these RFI cases regularly.  I only get involve in problem case, or
>> in this case when I am affected at my home shack.
>>
>> It appeared to be coming from the direction of the161KV line that runs
>> East-West; however, when the tech was using our new HF loops we had the
>> same perpendicular indications no matter which direction we traveled.  It
>> was staying strong for 1 to 2 miles in each direction before beginning to
>> fade.  Our mistake was to stay too focused on using HF freqs for tracking
>> that day, but we were also initially confused by the southwest direction we
>> got at the ham's QTH 1.5 miles north of the 161KV line.  We only switched
>> to VHF/UHF in the area to the southwest finding nothing there.
>>
>> We unknowingly drove past the actual source directly south of both ham's
>> QTHes a few times not realizing this before ending our search at the end of
>> the work day (techs are union, no OT on RFI cases).
>>
>> The actual source turned out to be a distribution pole on a 13.8KV line
>> that ran parallel with the 161KV line for a short distance as it crossed
>> over the main street perpendicular to both lines to reach a couple houses
>> on that street.  The RFI source was apparently causing induction into the
>> 161KV line from the shorter 13.8KV line.
>>
>> We never had to track the source down to fix it.  On my way home from the
>> office that same day, as I drove toward the 161KV line while listening to a
>> blank spot on my AM radio, it appeared the noise was already gone!  As I
>> approached the 161KV line I see a couple of our utility trucks working to
>> install a new pole replacing one of the old poles on the line that ran
>> parallel under the 161KV line.  Since the noise never returned, I assume
>> the old pole that was replaced was our source pole.
>>
>> Some days you just get lucky!
>>
>> 73, de ed -K0iL
>>
>> -----Original Message-----
>> From: RFI <rfi-bounces+eedwards=oppd.com at contesting.com> On Behalf Of Don
>> Kirk
>> Sent: Tuesday, March 9, 2021 6:27 PM
>> To: RFI <rfi at contesting.com>
>> Subject: [RFI] Difficult power line RFI find.
>>
>> Just thought I should share something that was a first for me when
>> tracking down power line RFI and man it was frustrating, and I have tracked
>> down a lot of powerline RFI.
>>
>> I noticed some weak RFI at Dans (KB9AX) on 160 meters earlier this year
>> but did not have time to track it down.  Dan also complained about the RFI
>> and he mentioned this week that it was not strong but had become very
>> consistent.  It definitely looked and sounded like powerline noise (120 Hz
>> spikes observed on audio scope and SDR receiver, etc.)  ---snip---
>>
>>
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-- 
Scott  K9MA

k9ma at sdellington.us