Thanks Eddie.
My utility is small with no RFI experience that I know of. They call
TVA. My last TVA visit years ago was like this; Took weeks (months?) to
visit. They arrive and the noise is absent but appears while they are
off out of sight. They go off in directions my beams were not
indicating. Give little credence as to the pole I suspected. Mention
they don't have much time. Wont mention if they will be back. I got the
vibe they did not want to be here. Seem unfamiliar with the gear they
have. When asked if they will come back do not say. Etc. It made me so
angry I channeled that anger into learning more myself. Found it myself
(on the pole I suspected) and my local utility fixed it. May have been
about the time I built the ultrasonic dish, do not remember.
Contrast to last April. I hunted that source day and night for months to
make sure (would have been less time but i had other constraints on my
time). Located it with methods you, others, and I mentioned. Took
picture of the request with area circled and other details and emailed
it to the power co engineer. They fixed in about a week or less.
As I say, the TVA visit was years ago. From recent emails with one of
them, I am hopeful things are better but really hesitant to depend on
it. I know things are much better with my local utility. Night and day
now (long story). And I fully realize they are way to small to have an
onsite RFI tech. An education initiative like Ed Hare mentioned I hope
will be a improvement in the utilities knowing their responsibilities
and what is not their responsibility. Even if my utility bought some
radar engineers ultrasonic gear that would be huge for me. Even a pole
mounted ultrasonic sniffer would be huge since that much pinpoint is
usually where I run into a roadblock. I'm not an employee but would be
happy to help them understand it. I mentioned this once but no response
to my email, lol.
I just about salivate over the Radar Engineers gear like high dollar
transceivers.....
My dish (QST article hombrew) though seems to be working well.
Yesterday, unfortunately I could not hear suspect pole #2's source but
one side of the pole I could not get too as it borders a yard that a
renter recently left and its grown up like a jungle including vines and
scrubby tree limbs reaching the drop lines to the houses. The other side
is city park so no issue there. Not much on the pole but the drops, a
transformer, and single phase run. Luckily all the close by poles with
the 7.2kv are either on right of ways or in the park so I can somewhat
access them without trespassing.
Coming back I listened to a pure sinewave sounding tone coming out of a
CATV box, a bird cleaning its feathers sitting on the line, my feet
walking on the grass, source #1 still singing, etc so think the dish is
good.
I do have a phenomenon with the dish. May post in a separate thread. I
need to do more leg work and gather more data. But the last 3 sources I
have tracked, all three had certain levels of isolated undergrowth. One,
had a crepe myrtle growing around the pole but otherwise the yard was
mowed. The second, a flat trailer by the pole with no bed that was grown
up but otherwise mowed. And the third, the yard grown up on one side of
the pole but mowed on the other.
Now here is the phenomenon. Whenever i get close to one of these poles,
when the arc is active, the dish goes into a odd oscillation of about
1-2hz. I can point all around but when I point into the thickest
undergrowth it gets the strongest. Where the grass is mowed I hear less
of it. For instance the one with the trailer, only in that small amount
of undergrowth do i hear this the loudest. Its not focused as much like
picking up an arc. I am very familiar with what an arc sounds like. Of
course the oscillation is an annoyance to try and hear the arc but I can
still hear it. Pointing up at the arc, the oscillation is not near as
loud, only near the ground. The source currently active/strong with the
grown up backyard, I cannot get with about 50 feet of it before I start
hearing this oscillation.
Other poles, other undergrowth, trees, that i tried do not cause this
oscillation. The dish, when not near anything, normally has a very low
nice level background noise even with the volume all the way up. Maybe
the magnetic field off the arc is causing this. Maybe I need to put my
PC board on the dish in a metal box with feedthrough cap's. Not sure. Odd.
Chuck
W4NBO
On 10/1/21 1:14 PM, EDWARDS, EDDIE J wrote:
Excellent points Chuck!
You're not just a student. You are also an instructor with personal
experience yourself.
Back in the TVI days, utilities would have one or more full time RFI
investigators on staff. At my utility they rotated the radio
technicians around so they all got the experience. Some were better
than others. Today with cable TV and now digital TV and internet
streaming TV, the RFI complaints are very rare now. Last year we had
zero! And only 6 so far this year and half were sources in their own
homes. So they don't have a full time investigator anymore. This means
it's going to take longer to get them out, and it won't always be
there when they do. They sure don't want to pay overtime to have them
checking at nighttime as you found necessary sometimes.
So it is up to hams as self-educated, technical specialists to do the
early footwork if they want RFI located quickly.
Hopefully when I retire next year, my employer will take me up on an
offer to be an RFI consultant for them. That's why I purchased a new
Radar Engineers 243 for the techs to use and for me to borrow! :-)
73, de ed -K0iL
Eddie Edwards, P.E.
Business Technology - DTS
Omaha Public Power District
4302 Jones Plaza, Omaha NE 68105-1099
eedwards@oppd.com
-----Original Message-----
From: RFI <rfi-bounces+eedwards=oppd.com@contesting.com> On Behalf Of
Charles Plunk
Sent: Wednesday, September 29, 2021 4:40 PM
To: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] CASE HISTORY - Powerline - Multiple Sources
(re-post w/o errata)
Yes, great list.
That maybe me on #2, lol. I re-transmit the audio from the HF receiver
on 440 while DFing on 2m or vica versa with 2 HT's. Could be done with
one dual bander I suppose as long as you can listen to both bands at
the same time. Seems like nearly all my 120hz noise at some point will
develop a distinctive pattern especially as the weather changes but
one has to be really patient for this method. Got to be ready to go
when it does happen, usually at a non convenient time. But when it
does, its obvious by listening to the two sources that you have a match.
It helps also to have a rotatable vhf (or possibly uhf) station beam
to get you started in the right direction. Listening to the pattern
(especially if its intermittent) on vhf and hf at the same time to match.
And you maybe able to actually see the arc at night especially with
binoculars once you have found the pole. Of course it helps if its
dark and no nearby streetlights. Likely expect a faint little pinpoint
arc.
Just more tools to consider. One has to keep a really open mind
chasing this stuff and get all your ducks in a row before calling the
utility.
It is really time consuming for me but worth it and really satisfying
when the utility fixes the source you found. Kind of like solving a
complex puzzle. And can be very frustrating at the same time for many
reasons.
The knowledge base on this reflector is incredible. I am happy to be a
student here.
Currently chasing 3 sources. I have identified all 3 poles and got one
pinpointed with the Ultrasonic. The other 2 are intermittent to the
point of ceasing for weeks and months at the time making the hunt long
term. One of these I identified today. Its 2 houses down and singing
like a canary. The pattern matched. Not long after I got back to the
shack it ceased so no Ultrasonic for now....
73
Chuck
W4NBO
On 9/29/21 10:50 AM, EDWARDS, EDDIE J via RFI wrote:
Alan,
Sorry for my delayed post on this subject. Some things previously
mentioned on this group by the professional RFI investigators who
have posted in the past but I wasn't sure if you were aware of in
your post:
1. In older neighborhoods with older power lines, you should be able
to find dozens and maybe over 100 RFI sources within a short distance
to your station. Not all of them are creating RFI being picked up at
the location of you antenna(s). And the utility is not required to
fix all of them if they are not causing harmful interference to anyone.
2. Best way to verify that a source in the field is your RFI source on
your radio is to get a noise signature on a scope, save it on the
scope, then go into the field and find a matching noise signature in
the field. One ham on the list has done this using his ears, but most
of us with tinnitus need visual scope readings. LOL
3. If you let multiple sources ramp up, you will be "pealing the
onion" as you remove the loud sources first only to find less strong
ones below that layer. You may have found this to be the situation in
your case.
4. Back in the pre-cable, pre-streaming TV days, it was the utilities
responsibility to find and repair RFI sources causing interference to
TV or radios. It is to their benefit to perform their work tasks in
the most efficient way possible. So it is to their benefit to have
trained and well equipped RFI investigators. Not all utilities will
be this efficient as you have found. Utility's budgets and internal
politics can interfere with these tasks. But the FCC's viewpoint is
that it is the utilities responsibility to find and eliminate harmful
interference from their equipment and only their equipment. The ham
should only verify that it is from the utility's equipment and not
his own or his neighbors'.
5. Always continue to listen at higher and higher frequencies when
searching for RFI sources on powerlines. You should be able to
confirm a source by finding it at 300Mhz or higher. If you cannot
hear it that high, keep moving down the line until it gets stronger
or fades away. And it is possible it is not from the utility
equipment at all if it is not broadband noise.
73, de ed -K0iL
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