I'm afraid the email below is just repeating an error about how loop
antennas work. (They say if you hear something repeated enough times it
is is perceived as truth). But not so. For an excellent paper on how
loop antennas work see:
https://w8ji.com/magnetic_receiving_loops.htm
Ray, W4BYG
On 3/23/2021 19:16, Kenneth Wyatt via RFI wrote:
Tom,
The usual loop antenna design picks up magnetic fields, which tend to be
dominant from SMPS transformers and inductors.
Cheers, Ken
________________
Ken Wyatt
wyattphoto@mac.com
On Mar 23, 2021, at 1:11 PM, rfi-request@contesting.com wrote:
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Today's Topics:
1. Re: New Interference at kk0sd (Tom Thompson)
2. Re: New Interference at kk0sd (Don Kirk)
----------------------------------------------------------------------
Message: 1
Date: Tue, 23 Mar 2021 12:27:45 -0600
From: Tom Thompson <w0ivj@tomthompson.com>
To: Mike Martin <mike@rfiservices.com>, Gary
<gary_mayfield@hotmail.com>
Cc: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
Message-ID: <fff7cac5-fe47-3b8a-20f1-349436e51149@tomthompson.com>
Content-Type: text/plain; charset=utf-8; format=flowed
See:? http://tomthompson.com/radio/ReceivingLoop/loop.html? for a tuned
loop.? You can build one in a couple of hours from your junk box.? This
type of loop does not work well for power line noise ( a vhf yagi is
better for that), but it does work well for switch mode RFI.? Since most
of these noise sources are vertically? polarized, look through the loop
for the null and along the edge for the peak. When close to the source,
the polarization may switch.
73,?? Tom?? W0IVJ
On 3/23/2021 6:32 AM, Mike Martin 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 ?
On Mar 22, 2021, 11:37 PM, at 11:37 PM, Gary <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@contesting.com> On
Behalf Of Kim Elmore
Sent: Monday, March 22, 2021 4:44 PM
To: Don Kirk <wd8dsb@gmail.com>
Cc: Rfi List <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> 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> 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 - W?LEV
On Mon, Mar 22, 2021 at 2:28 AM Kim Elmore
<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>
Sent: Sunday, March 21, 2021 6:53 PM
To: Gary <gary_mayfield@hotmail.com>
Cc: 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>
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:
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
________________________________
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RFI@contesting.com<mailto:RFI@contesting.com>
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_______________________________________________
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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./
_______________________________________________
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--
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*Just Let Darwin Work*
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------------------------------
Message: 2
Date: Tue, 23 Mar 2021 15:11:11 -0400
From: Don Kirk <wd8dsb@gmail.com>
To: Mike Martin <mike@rfiservices.com>
Cc: Gary <gary_mayfield@hotmail.com>, Kim Elmore
<cw_de_n5op@sbcglobal.net>, Rfi List <rfi@contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
Message-ID:
<CAKtW65d94DMhbd3RW8eP9Q8XaiK9Y5Yr-HOiyz6rD5vqar3vhw@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
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> 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> 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@contesting.com> On Behalf Of
Kim Elmore
Sent: Monday, March 22, 2021 4:44 PM
To: Don Kirk <wd8dsb@gmail.com>
Cc: Rfi List <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> 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> 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 - W?LEV
On Mon, Mar 22, 2021 at 2:28 AM Kim Elmore <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>
Sent: Sunday, March 21, 2021 6:53 PM
To: Gary <gary_mayfield@hotmail.com>
Cc: 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>
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:
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
------------------------------
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http://lists.contesting.com/mailman/listinfo/rfi
------------------------------
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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./
------------------------------
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http://lists.contesting.com/mailman/listinfo/rfi
--
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*Just Let Darwin Work*
------------------------------
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------------------------------
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------------------------------
End of RFI Digest, Vol 218, Issue 27
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