Hi Dave,
The W7IUV preamp is a great preamp and it actually works just fine with a 9
volt alkaline battery for portable use and it's what I've historically used
with my tuned loops and portable flag. Biggest problem now is procuring
authentic 2N5109 transistors.
Here is a link to my website that documents my W7IUV builds that show the
simple circuit boards I made using a dremel tool with cutoff wheel, etc.
https://sites.google.com/site/rxpreamps/
Just FYI,
Don (wd8dsb)
On Wed, Mar 24, 2021 at 4:22 PM David Eckhardt <davearea51a@gmail.com>
wrote:
> 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> 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> 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>
>> > *Sent:* Tuesday, March 23, 2021 4:34 PM
>> > *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
>
>
>> >
>> >
>> >
>> > 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> 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>
>> 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 - WØLEV
>> >
>> > 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
>> >
>>
> > ------------------------------
>> >
>> >
>> >
>> > 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
>> >
>> > --
>> >
>> > 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
>> > http://lists.contesting.com/mailman/listinfo/rfi
>> >
>> >
>> >
>> >
>> > --
>> > *Dave - WØLEV*
>> > *Just Let Darwin Work*
>> >
>> > ------------------------------
>> >
>> >
>> > 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
>> >
>> > ------------------------------
>> >
>> >
>> > RFI mailing list
>> > RFI@contesting.com
>> > http://lists.contesting.com/mailman/listinfo/rfi
>> >
>> >
>> _______________________________________________
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>> http://lists.contesting.com/mailman/listinfo/rfi
>>
>
>
> --
> *Dave - WØLEV*
> *Just Let Darwin Work*
>
>
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