[RFI] New Interference at kk0sd
Gary
gary_mayfield at hotmail.com
Wed Mar 24 22:48:34 EDT 2021
Very neat to learn – I will keep everyone posted.
73,
Joe kk0sd
From: Don Kirk <wd8dsb at gmail.com>
Sent: Wednesday, March 24, 2021 1:01 PM
To: Gary <gary_mayfield at hotmail.com>
Cc: Mike Martin <mike at rfiservices.com>; Kim Elmore <cw_de_n5op at sbcglobal.net>; Rfi List <rfi at contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
Hi Gary,
Thanks for the update, and I also went crazy today and ran more tests using my version of your un-tuned shielded loop. I always enjoy learning, and your situation is interesting and I have never used a shielded un-tuned loop based on the design you are using so this has been interesting.
Today I installed a full size 1/4 wave 20 meter vertical over my 55 buried ground radial field. I set up a transmitter 290 feet from this antenna (used my NanoVNA as the remote signal source on 14 MHz). The signal measures S6.1 on my TS-180s transceiver connected to my full size 1/4 wave 20 meter vertical and if I switch to the un-tuned loop using it in my shack with my TS-180s I can still hear the signal just fine but the S meter is not moving (S0) but it's easy to hear and it nulls in the correct direction. I can also easily hear this remote signal using my portable receiver outside my house with my version of your un-tuned loop (not very strong but I can easily hear it), and if I walk down my street even further away from the signal source I can still easily hear it and null it. While the sensitivity of your un-tuned loop is not good compared with most of the radio direction finding antennas we all use (tuned loops, etc) as we have all mentioned, it behaves really well on 14 MHz (sensitivity a bit better than a simple 9 inch un-tuned loop, and it has very nice balance).
This goes right back to the issue Kim and I were struggling with. The signal is so strong on 14 MHz at your location based on your recording (peaking 20 dB over S9) that it's hard to believe you can't hear it with your un-tuned loop.
Lots of great comments from everyone, and hope in the future you undertake some of the other direction finding antenna projects folks have mentioned, but based on the data you have supplied and based on my testing, it sure looks like your un-tuned loop should be hearing the noise while standing on your property or your antenna is generating it's own noise or there is a very local source (something sitting very, very close to your vertical that only your vertical can hear, etc.), or your portable receiver is not working right, or your un-tuned loop is broken, etc.
I can't wait to find out what the root cause of your problem is, as we will all learn a lot.
Have a great work week, and I now have to go put my 68 foot base loaded vertical that I use on 160 meters back up that I took down for todays experiments.
73,
Don (wd8dsb)
On Tue, Mar 23, 2021 at 6:20 PM Gary <gary_mayfield at hotmail.com<mailto:gary_mayfield at 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 at gmail.com<mailto:wd8dsb at gmail.com>>
Sent: Tuesday, March 23, 2021 4:34 PM
To: Mike Martin <mike at rfiservices.com<mailto:mike at rfiservices.com>>
Cc: Gary <gary_mayfield at hotmail.com<mailto:gary_mayfield at hotmail.com>>; Kim Elmore <cw_de_n5op at sbcglobal.net<mailto:cw_de_n5op at sbcglobal.net>>; Rfi List <rfi at contesting.com<mailto:rfi at 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 at gmail.com<mailto:wd8dsb at 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 at rfiservices.com<mailto:mike at 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
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On Mar 22, 2021, at 11:37 PM, Gary <gary_mayfield at hotmail.com<mailto:gary_mayfield at 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 at gmail.com<mailto:wd8dsb at gmail.com>>
Cc: Rfi List <rfi at contesting.com<mailto:rfi at 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 at gmail.com<mailto:wd8dsb at 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 at gmail.com<mailto:davearea51a at 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 at sbcglobal.net<mailto:cw_de_n5op at 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 at rfiservices.com<mailto:mike at rfiservices.com>>
Sent: Sunday, March 21, 2021 6:53 PM
To: Gary <gary_mayfield at hotmail.com<mailto:gary_mayfield at hotmail.com>>
Cc: rfi at contesting.com<mailto:rfi at 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>
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On Mar 21, 2021, at 2:01 PM, Gary <gary_mayfield at hotmail.com<mailto:gary_mayfield at hotmail.com><mailto:
gary_mayfield at hotmail.com<mailto:gary_mayfield at 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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CCM, PP SEL/MEL/Glider, N5OP, 2nd Class Radiotelegraph, GROL)
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*Dave - WØLEV*
*Just Let Darwin Work*
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