Thanks Don!
Very good to know. The preamp/attenuator combo sounds like a good idea!
73,
Joe kk0sd
From: Don Kirk <wd8dsb@gmail.com>
Sent: Thursday, March 25, 2021 6:33 AM
To: Gary <gary_mayfield@hotmail.com>
Cc: David Eckhardt <davearea51a@gmail.com>; Rfi List <rfi@contesting.com>
Subject: Re: [RFI] New Interference at kk0sd
Hi Gary,
You might also consider the DX Engineering preamp which offers about 10 dB more
gain than the W7IUV preamp and it has built in attenuators which come in very
handy as you approach the source, and it also has a AM broadcast band filter.
I tried my version of your shielded loop with the DX Enginering preamp and it
works really well, and the DX Engineering preamp has become my favorite preamp
for use with all my portable DF antennas. Here is a link to that preamp:
https://www.dxengineering.com/parts/dxe-nl-pre-att-1?rrec=true
Just FYI,
Don (wd8dsb)
On Wed, Mar 24, 2021 at 10:56 PM Gary
<gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com>> wrote:
Thank you Dave!
I stumbled across the same circuit here:
http://www.mtmscientific.com/preamp.pdf
It is one of the things I will do this weekend. Luckily I have the parts on
hand and will put it on a little prototype board.
Thanks and 73,
Joe kk0sd
From: David Eckhardt <davearea51a@gmail.com<mailto:davearea51a@gmail.com>>
Sent: Wednesday, March 24, 2021 3:23 PM
To: Don Kirk <wd8dsb@gmail.com<mailto:wd8dsb@gmail.com>>
Cc: Gary <gary_mayfield@hotmail.com<mailto:gary_mayfield@hotmail.com>>; Rfi
List <rfi@contesting.com<mailto:rfi@contesting.com>>
Subject: Re: [RFI] New Interference at kk0sd
While not my design, this works wonders for the small untuned loops. I used a
2N5109. Don't fudge too much on the component values as the author points out
the values presented yield good dynamic range. The dynamic range is quite
impressive (lack of IM). I'll also include a response curve. Yellow:
Straight through with no preamp. Lavendar: With preamp @ 15 vdc. Nominal
gain is pretty flat from 10 kHz (and lower) through 30 MHz. It does roll off
at 50 MHz. I used 25 total turns to enhance the low end. You will need to
heat sink the transistor with a clip-on black heat sink. It should draw
between 70 and 80 mA on 12 VDC and 90ish at 15 VDC. You should experiment with
core material, but I used a core specifically mixed for ELF through MF.
Moderator: Please also post this under the 'LOOP' "hijacked" subject line.
Dave - WØLEV
On Wed, Mar 24, 2021 at 6:05 PM Don Kirk
<wd8dsb@gmail.com<mailto:wd8dsb@gmail.com>> wrote:
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@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: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: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: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<mailto:hotmail.com@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>>
> Cc: Rfi List <rfi@contesting.com<mailto: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: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>> 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>> 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>>
> Sent: Sunday, March 21, 2021 6:53 PM
> To: Gary <gary_mayfield@hotmail.com<mailto: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:gary_mayfield@hotmail.com><mailto:
>
> 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
>
> ------------------------------
>
>
>
> RFI mailing list
>
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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
>
>
>
>
> --
> *Dave - WØLEV*
> *Just Let Darwin Work*
>
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>
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>
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>
>
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