This thread is a beautiful illustration of how useful information can
get lost when a thread is hijacked. Ed's very informative post about
small loop DFing was hidden under "New interference at KK0SD." Please,
when you take a thread off on a tangent, rename it, with a "'was:" link
back to the original topic.
73, Pete N4ZR
Check out the new Reverse Beacon Network
web server at <http://beta.reversebeacon.net>.
For spots, please use your favorite
"retail" DX cluster.
On 3/24/2021 8:01 AM, Gary wrote:
Thank you Ed! Good information!
73,
Gary “Joe” kk0sd
From: Hare, Ed, W1RFI <w1rfi@arrl.org>
Sent: Wednesday, March 24, 2021 1:28 AM
To: David Eckhardt <davearea51a@gmail.com>; Gary <gary_mayfield@hotmail.com>
Cc: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
There are a few things to remember about using a small loop for DFing on HF. For "point
sources," such as a device in a home being heard from the street, small loops can work well.
I remember years back, when a "wireless modem jack" product was introducted into the
market, operating on frequencies near 3.56 MHz, I had brougth a small receiver and a small 80-m
loop I had designed, using a ferrite rod, on a business trip. I was a hotel and my room had a
small balcony, so I took the receiver and loop onto the balcony, to hear what I could hear.
As I tuned the band, pleased that this little resonant loop could hear signals,
to my surprise, I heard a T7 carrier on 3.56 MHz, characteristic of the
wireless modem jack. I had a rental car, so I decided to find it. I got a
heading on its general direction by finding the null and knew it was located on
one of two headings. I took a ride and went about a half mile perpendicular to
the heading (more or less) and still heard the signal, so I took a new heading
and now knew which direction it was.
I drove to that area and, with a bit of driving around and taking new headings,
I got to the house.
As I drove past the house, I could keep the null pointed at the house and watched
the heading change as I drove past it. It was clear that the house wiring was
doing most of the radiating, so there was a sharp-enough null. And, for the
record, this was heard from my hotel balcony about a mile from where it was
located, so these devices were WAY above the FCC emissions limits for
carrier-current devices. ARRL worked with the manufacturer to redesign the product
to no longer use the ham bands. AT&T had bought them and installed them by the
thousands in conjunction with its pay-per-view cable television service, and they
ended up doing a system-wide recall of them, so the whole story is interesting in
and of itself.
In another case, though, I used it to try to DF a power-ine noise. It was very
strong, so from afar, I could get a heading, but when I got close, I couldn't
really find a meaningful null. In the first example, the house wiring acted
like a point source, but the power-line noise was radiating from a long length
of overhead wiring, with standing waves and other complicating factors. When I
was close, no matter where I pointed the null, there was signal coming in at
many angles from the null, so there was no null.
The moral of the story is that there are some types of noise sources in which
one cannot find a heading with a loop antenna.
But all is not lost. I remember another case I went out on, loopless. A ham
had a strong 80 meter source, and he had driven around to find out where it was
coming from. I was in the general area on another IEEE meeting trip, but all I
had was my HF mobile set up. I drove to where he said it was coming from, but
it was across a small river and there were no overhead wires on the bridge, so
driving away from his house, the noise disappeared completely and noise was
heard again on the other side of the river. It sounded different, too,
meaningful ONLY if it sounds different. By ear, dissimilar noises can sound the
same.
I went back to his house. I could hear it from his driveway, so I went off in
another direction. There was a standing wave on the line. I got a quarter mile
away and there was a side road to my right, and as I drove past that side road,
the noise started geting weaker, again in peaks and nulls, but clearly
disappearing. Back to the side road and as I drove the road, it got louder and
louder with peaks and nulls, until I got to a section of road whee it screamed
so loud all I could tell is that it somewhere along about 0.2 miles of overhead
line.
I had a step attenuator, so I decided to try a trick. I drove to about where I
thought it was strongest. I listended to the raucous buzz (120 Hz) and cranked
in attentuation until the buzz dissapeared and all I heard was white noise from
the receiver. I cranked back until I could JUST barely hear the buzz over the
white noise of the receiver. My ear was pretty good at that. I again drove
the line and heard it louder as I drove past a certain pole. I stopped at the
pole, cranked in attenuation until it was just audible and sure enugh, it was
heard only driving past that pole.
I looked around and there was a small commercial building to my left, with 240
volt wiring running to the pole transformer. I drove up the driveway and as I
got near the building, it got louder. I laughed as I looked at the building
name -- Acme Welding.
What I realized was a few things. First, one can be misled driving around and
hearing noises. If that noise is strong at your QTH, but disappears when you
drive away, but noise reappears some distance away, it is probably a different
noise you can't hear from your station. Unless it is causing harmful
interference, the power company does NOT need to fix it. If you find a dozen
noises within a few miles and ask the company to fix them all, you WILL wear
out your welcome and they, and the FCC, will think you are on a crusade against
noise. Find and report only noises you hear, and keep in mind how easy it is
to be misled.
But the moral of the story is that very strong noise sources come from everywhere,
although if I had a loop near that welding shop, although it was being radiated strongly
by the overhead line and there was no deep null, it was also being radiated by the shop
wiring, thee may have been some null. But from the street, the noise was heard from the
overhead line, from the radiation of the ground wire on the pile to my vertical whip and
from the building. They would have added up to a vector angle that may have
"pointed" at some location other than the building. But I had deciced to try
the step attenuator and use of my trained ear to pinpoint the souce, and, to my surprise,
it actually worked.
I also noted two things. When I was near the source, some of the noise was
coming from the building wiring. This decayed rapidly with distance. But when
it got coupled onto the overhead lines, it was also radiated by a large wire,
so decayed at the well-known inverse square law perpendicular from the line,
but beause the overhead lines were a leaky transmission line, it traveled along
that line for quite some distance.
Okay, those are my experiences. Use them as you will, but note all the caveats
that to really find the souce this way, I had to combine several bits of
knowledge.
Ed Hare, W1RFI
ARRL Lab
________________________________
From: RFI
<rfi-bounces+w1rfi=arrl.org@contesting.com<mailto:rfi-bounces+w1rfi=arrl.org@contesting.com>>
on behalf of David Eckhardt <davearea51a@gmail.com<mailto:davearea51a@gmail.com>>
Sent: Tuesday, March 23, 2021 6:29 PM
To: Gary <gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com>>
Cc: Rfi List <rfi@contesting.com<mailto:rfi@contesting.com>>
Subject: Re: [RFI] New Interference at kk0sd
Another trick I've used in DFing interference is to construct a shortened
helically wound dipole on a wooden dowel stick. One can easily resonate it
for the frequency of interest by extending / trimming the pigtails at the
high-Z end of each helical winding. While the null of the ends is not as
sharp as with the shield loops, it gets the job done and is extremely
narrow in response.
Dave - WØLEV
On Tue, Mar 23, 2021 at 10:20 PM Gary
<gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com>> wrote:
Don,
I hope to hook the loop to my FT-847 this weekend as it is
on my list of tests. It is a little more involved to do. I don’t hear much
in general with antennas in my basement shack…I probably have more faith in
the loop than my portable shortwave radio. I am glad to hear the loop works
okay on the shortwave bands. I use a ferrite antenna for the AM band when I
hear noise there. It still amazes me I do not hear anything on the AM
broadcast band. The good news is I did hear the noise when connecting my
portable shortwave to my main antenna…
I have also arranged to borrow an FT-818 for portable
chasing this weekend. I hear the noise on 6 meters (but not 2 meters) so I
am hoping with the portable rig and a 6 meter beam I can at least get
pointed in the right direction.
Thank You Everyone for the Help!
73,
Gary “Joe” kk0sd
From: Don Kirk <wd8dsb@gmail.com<mailto:wd8dsb@gmail.com>>
Sent: Tuesday, March 23, 2021 4:34 PM
To: Mike Martin <mike@rfiservices.com<mailto:mike@rfiservices.com>>
Cc: Gary <gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com>>; Kim Elmore
<cw_de_n5op@sbcglobal.net<mailto:cw_de_n5op@sbcglobal.net>>;
Rfi List <rfi@contesting.com<mailto:rfi@contesting.com>>
Subject: Re: [RFI] New Interference at kk0sd
Hi Gary and gang,
Let me go back and clarify my previous statement about your shielded loop
as I just did more testing on higher frequencies. Down in the AM broadcast
band your loop based on my using RG-58 is deaf compared with a simple 9
inch single turn loop, but on higher frequencies its sensitivity greatly
improves (I even thought the sheild on my RG-58 might be inadequate down in
the AM broadcast band so I added aluminum foil as a secondary shield and
that had no impact. Up on 10 and 15 MHz I would say the gain of my
version of your shielded loop is much closer to that of my simple 9 inch
diameter loop but I did not dig out my test gear to see how close they
really were, but I did like how the shielded loop was behaving on the
higher frequencies. I'm not sure what any of the numbers mean because
there is no attention paid to impedance matching, etc.
I went back and looked at your original video and on 20 meters the RFI is
very strong, and I can't believe you can't hear it with your shielded loop
based on some signal strength measurements I did today (maybe your portable
radio is deaf????). I can just barely hear WWV on 10 MHz using my version
of your shielded loop when WWV is running about S7 on my HF rig that's
using an antenna that's resonate on 10 MHz (during the afternoon).
I really am curious what you would hear on 20 meters if you just connect
your shielded loop to your HF rig. If it's easy to do it would be great if
you could do this with your shielded loop outside (maybe just connect the
shielded loop to your coax that's currently going to your vertical.
Sorry I have probably gotten you way off track.
Don (wd8dsb)
On Tue, Mar 23, 2021 at 3:11 PM Don Kirk <wd8dsb@gmail.com<mailto:
<mailto:wd8dsb@gmail.com%3cmailto:%0b>>
wd8dsb@gmail.com<mailto:wd8dsb@gmail.com>>> wrote:
Hi Mike, Gary, and gang,
Well after seeing Garys shielded un-tuned loop, I watched the video on how
to build that loop. I just built one almost identical to his loop but used
RG-58 coax since that's what I had on hand. I also spent 10 seconds
building a simple 1 turn 9 inch loop (no form, just free standing) for
comparisons which is even smaller than Garys loop, and I can tell you there
is no comparison. Without doing any impedance matching, the 9 inch
un-tuned single turn loop I built has a gain that is approximately 23 dB
greater than Garys loop when tested in the AM broadcast band and it still
exhibits nice nulls which comes as no surprise. My single turn non
shielded loop just has about 6 inches of twisted wire (the same wire that
forms the loop) to form the feedline to it, and then I just used a 3 foot
piece of 50 ohm coax to connect it to my receiver. I used the same 3 foot
piece of coax to connect the shielded un-tuned loop to the receiver. While
my un-tuned 9 inch loop might not be as well balanced (one null might be
deeper than the opposite null), it makes one fine DF antenna in a pinch.
Also if Gary needs more gain he can just make the loop I made bigger in
diameter. It really just takes seconds to make this antenna (much less
than a minute).
I now fully understand why Gary can't hear his noise, as his un-tuned
shielded loop has very poor sensitivity based on my trying to copy the
design. While I normally use preamps with my DF loops, Garys RFI is so
strong that I'm pretty darn sure he can make a simple one turn loop to
figure out what possible directions the signal is coming from. Something I
have done in the past is to use a cardboard box as the antenna form as it
does not have to be round. Need to figure out what directions the signal
is coming from before leaving his property if at all possible.
Just my opinion, and I will try and post some comparison videos but they
will not be pretty as I'm buried in other tasks.
73,
Don (wd8dsb)
On Tue, Mar 23, 2021 at 8:33 AM Mike Martin <mike@rfiservices.com<mailto:
<mailto:mike@rfiservices.com%3cmailto:%0b>>
mike@rfiservices.com<mailto:mike@rfiservices.com>>> wrote:
Remember in his shack he has a very good radio and a very good antenna
which together increased sensitivity and allow him to hear much further
away. when he goes outside with a portable and a smaller antenna he doesn't
have the sensitivity he had inside there for he may have to travel a lot
further before he's able to receive it.
Be safe,
Mike
Get BlueMail for Android<http://www.bluemail.me/r?b=16696>
On Mar 22, 2021, at 11:37 PM, Gary <gary_mayfield@hotmail.com<mailto:
<mailto:gary_mayfield@hotmail.com%3cmailto:%0b>>
gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com>>> wrote:
Kim,
I hear it on the portable when connected to the vertical antenna, but
will undertake an antenna substitution experiment this weekend.
Keep the suggestions coming!
73 and Thanks,
Gary "Joe", kk0sd
-----Original Message-----
From: RFI <rfi-bounces+gary_mayfield=hotmail.com<http://hotmail.com>@
contesting.com<http://contesting.com>> On Behalf Of Kim Elmore
Sent: Monday, March 22, 2021 4:44 PM
To: Don Kirk
<wd8dsb@gmail.com<mailto:wd8dsb@gmail.com<mailto:wd8dsb@gmail.com%3cmailto:wd8dsb@gmail.com>>>
Cc: Rfi List
<rfi@contesting.com<mailto:rfi@contesting.com<mailto:rfi@contesting.com%3cmailto:rfi@contesting.com>>>
Subject: Re: [RFI] New Interference at kk0sd
That’s a great idea, too! I once ran into an interference problem that was
inherent to the antenna, but only under certain conditions. It didn’t sound
like Gary’s but I pulled a lot of hair out fixing that one. I’m simply
suspicious that he hears NOTHING with his portable rx so I’m after
eliminating anything inherent to his station. Standing by his vertical with
his portable rx is a great idea.
73,
Kim N5OP
"People that make music together cannot be enemies, at least as long as
the music lasts." -- Paul Hindemith
On Mar 22, 2021, at 2:24 PM, Don Kirk <wd8dsb@gmail.com<mailto:
<mailto:wd8dsb@gmail.com%3cmailto:%0b>>
wd8dsb@gmail.com<mailto:wd8dsb@gmail.com>>> wrote:
Hi Dave,
I still recommend tuned and untuned loops to folks on an almost daily
basis but they definitely don’t shed as much light on the situation as a
unidirectional antenna does. It would be nice to see what your shielded
untuned loop design is.
The beauty of the portable flag which is unidirectional is that you
typically can walk right to the source (no guessing which direction the
signal is coming from). I still pack 7 antennas when I go on a RFI case,
and this includes 3 tuned HF loops, but I have found that I typically don’t
use bidirectional loops anymore (unless I’m trying to be more stealth) as
the portable flag saves me an enormous amount of time. Also in heavily
congested areas (like downtown Indianapolis) having the unidirectional HF
antenna is priceless as it unmasks noise that’s mixing from other sources
that are in the opposite direction, etc. Yesterday I worked on a case
(more of a country setting) where I had 2 different bad poles that were
only 0.14 miles apart plus a 3rd RFI source generating spikes every 1 KHz
within the same area and having the unidirectional HF antenna helped me
locate all 3 sources in a matter of minutes (way under an hour).
You can never have enough antennas in your direction finding bag of
tricks but after using a unidirectional HF antenna like the portable flag
for direction finding I can’t imagine not using one. It typically takes me
seconds to tell which direction the signal is without the need of
triangulation, etc. Traditional triangulation has almost become a thing of
the past for me.
I also have been helping a ham that has the MFJ unit (the one with a beam
and the one with a dipole) and while it has helped him, it has an odd
characteristic that makes the meter jump which causes confusion to him and
after looking at the schematic I question how they implemented AGC in those
units. I’m starting to think AGC in a radio direction finding system is
typically not desirable. Manual attenuation is priceless but I don’t want
anything changing gain automatically.
Just my opinion from tracking down RFI on an almost continuous basis in
addition to my day job.
Please share details on your shielded untuned loop and thanks.
73,
Don wd8dsb
On Mon, Mar 22, 2021 at 1:22 PM David Eckhardt <davearea51a@gmail.com
<mailto:davearea51a@gmail.com%0b>> <mailto:davearea51a@gmail.com>> wrote:
We recently found a faulty lightning 'arrestor' on a pole by using
both the MFJ device and a small shielded loop (easy home brew
project) into a battery-powered receiver. We had two of us in the
field. One wielded the MFJ and I had the small (0.5-meter) shielded
loop fed into the Yaesu VR-500 on 1.830 MHz (160-meters). We both
independently found the same source / pole in the field. The null on
the shielded loop is extremely sharp and this piece of hardware
should be in the bag of tricks of anyone sleuthing RFI. It is a
powerful tool when coupled to a battery-powered receiver with its
extremely sharp null (perpendicular to the plane of the loop). One
doesn't need something as large as the 'Flag" that was recently published
in QST and referred to in a previous post in this thread. Another plus
for the shielded loop is that in the field, one can tune the receiver
to the worst-case frequency of the RFI as I did in the related story,
above.
The shielded loop is untuned. The MFJ relies only on VHF noise. In some
cases, an ultrasonic microphone at the focus of a small parabolic or
spherical reflector is good at finding coronal discharges as well as
active arcs and discharges. MFJ also makes that at a reasonable price.
Our power provider was out the next day to fix the problem. We even
gave them the pole number which is a great help to any power provider.
Dave - WØLEV
On Mon, Mar 22, 2021 at 2:28 AM Kim Elmore <cw_de_n5op@sbcglobal.net
<mailto:cw_de_n5op@sbcglobal.net%0b>> <mailto:cw_de_n5op@sbcglobal.net>> wrote:
It's odd that you can't hear it on your portable rx. That made me
curious: What if this is something internal to your '847? Have you
tried pulling your '847 and listening on a different receiver using
the same antenna? If you have, do you still hear the noise? It's a long
shot, but...
Kim N5OP
On 3/21/2021 7:28 PM, Gary wrote:
Mike,
Thanks for the info. I understand locating the
noise is
more important than identifying the noise. I am just try to play
all the angles as I was hoping to work the WPX contest nest
weekend. I have been walking the neighborhood a good chunk of the
afternoon, and have not been able to hear the noise on my portable
shortwave and loop antenna. It is as strong as ever on my home station.
I have an MFJ 852 Noise Finder and it seems to
go crazy
when broadside to any house. The neighbors on each side of me drive
the meter full scale.
Yep I only want to knock on one door, as I know
that
can get dicey. I would rather place a call to a utility, but can’t
really do either until I know.
Keep the suggestions coming!
Thanks and 73,
Gary “Joe” kk0sd
From: Mike Martin
<mike@rfiservices.com<mailto:mike@rfiservices.com<mailto:mike@rfiservices.com%3cmailto:mike@rfiservices.com>>>
Sent: Sunday, March 21, 2021 6:53 PM
To: Gary
<gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com%3cmailto:gary_mayfield@hotmail.com>>>
Cc: rfi@contesting.com<mailto:rfi@contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
Joe I haven't had time to read all the other input but I can tell
you it
is not an arcing source or a sparking source. either one of the two
would be much broader than what you're reporting. if someone were
to tell you exactly what it is you really wouldn't be any further
ahead. You would still have to find which residents or business
it's in. My suggestion would be to either go mobile or on foot,
preferably on foot listening to the frequency that you know the
problem affects. once you locate the residents then go through the
breaker scenario and locate what the source is. Be 100% certain of
the structure or home that the problem is in before knocking on the
door. The last thing you want to do is start guessing. Guessing we'll
ruin the relationship with your neighbors.
Be safe,
Mike k3RFI
www.rfiservices.com<http://www.rfiservices.com><
http://www.rfiservices.com>
Get BlueMail for Android<http://www.bluemail.me/r?b=16696>
On Mar 21, 2021, at 2:01 PM, Gary <gary_mayfield@hotmail.com<mailto:
<mailto:gary_mayfield@hotmail.com%3cmailto:%0b>>
gary_mayfield@hotmail.com><mailto<mailto:gary_mayfield@hotmail.com%3e%3cmailto>:
gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com%3cmailto:gary_mayfield@hotmail.com>>>>
wrote:
My last problem was tracked down to a neon sign in a neighbors
garage. I
had several months of blissful relatively low noise operation, but
now have a new RFI issue.
You can see a recording of it here:
https://www.youtube.com/watch?v=GKf4P44FXMo
I have turned all of the breakers in my home off and run the
radio from
a battery and the noise remains.
My neighborhood utilities are all underground.
There are no solar installations in my neighborhood, and the
noise is
there at night anyway...
The noise is not detectable on the AM broadcast band, but starts
around
2 MHz and runs to at least 6 meters.
It is there 7 days a week 24 hours a day.
It is not detectable from my pickup when I drive the streets of
my
neighborhood (checking both AM broadcast and Shortwave).
If any one has heard something like this, I would love to hear
what you
found.
Thank You for your input and help!
73,
Gary "Joe", kk0sd
________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com><mailto:RFI@contesting.com
<mailto:RFI@contesting.com>>
http://lists.contesting.com/mailman/listinfo/rfi
________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
--
Kim Elmore, Ph.D. (Adj. Assoc. Prof., OU School of Meteorology,
CCM, PP SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)
/"A great second violinist plays second fiddle to no one." //– Robert C.
Marsh, Chicago Sun-Times./
________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
--
*Dave - WØLEV*
*Just Let Darwin Work*
________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
--
*Dave - WØLEV*
*Just Let Darwin Work*
_______________________________________________
RFI mailing list
RFI@contesting.com<mailto:RFI@contesting.com>
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|