[RFI] New Interference at kk0sd
Gary
gary_mayfield at hotmail.com
Tue Mar 23 21:30:24 EDT 2021
I have access to the article. I am looking at it now. I think I have the variable cap in my junk box.
Thanks and 73,
Gary "Joe" kk0sd
-----Original Message-----
From: K9MA <k9ma at sdellington.us>
Sent: Tuesday, March 23, 2021 8:08 PM
To: Gary <gary_mayfield at hotmail.com>
Cc: David Eckhardt <davearea51a at gmail.com>; Rfi List <rfi at contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
See September 1995 QST for an article I wrote on a very simple way to match a small tuned loop. It takes just two capacitors. Email me off list if you don't have access to QST archives.
73,
Scott K9MA
----------
Scott Ellington
--- via iPad
> On Mar 23, 2021, at 5:23 PM, Gary <gary_mayfield at hotmail.com> wrote:
>
> Thanks Dave! Another weapon for the arsenal.
>
> 73 and Keep the ideas coming!
> Gary “Joe” kk0sd
>
> From: David Eckhardt <davearea51a at gmail.com>
> Sent: Tuesday, March 23, 2021 5:30 PM
> To: Gary <gary_mayfield at hotmail.com>
> Cc: Don Kirk <wd8dsb at gmail.com>; Mike Martin <mike at rfiservices.com>;
> Rfi List <rfi at 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 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><mailto: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><mailto: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
> Get BlueMail for Android<http://www.bluemail.me/r?b=16696>
> On Mar 22, 2021, at 11:37 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:
>
> 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><http://hotm
> ail.com>@contesting.com<http://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><mailto:wd8dsb at gmail.com<mai
> lto:wd8dsb at gmail.com>>>
> Cc: Rfi List
> <rfi at contesting.com<mailto:rfi at contesting.com><mailto:rfi at contesting.c
> om<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><mailto: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><mailto: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><mailto: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><mailto:mike at rfiserv
> ices.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><mailto:ga
> ry_mayfield at hotmail.com<mailto:gary_mayfield at hotmail.com>>>
> Cc:
> rfi at contesting.com<mailto:rfi at contesting.com><mailto:rfi at contesting.co
> m<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><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 at hotmail.com<mailto:gary_mayfield at hotmail.com><mailto:gary_mayfield at hotmail.com<mailto:gary_mayfield at hotmail.com>><mailto:
>
> 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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> --
>
> 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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>
>
> --
> *Dave - WØLEV*
> *Just Let Darwin Work*
>
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> Just Let Darwin Work
>
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