Training Notes: HF NVIS Antennas

In the last Radio Contra I discussed a simple way of rigging up an antenna for NVIS HF use. Its a topic that gets a lot of attention, and in turn, a lot of confusion. But trust me, its simple. The whole point behind HF is creating regional communications- anything that’s beyond line of sight– and while you can spend a heck of a lot of money in a hurry and not get a lot, you can spend just a few bucks and with a little knowhow I’m about to impart here, have a great setup.
NVIS relies on sending as much of your radiated energy skyward as possible, with as close to a zero degree takeoff as possible. So, this means a horizontal antenna close to the ground. In case you’re wondering, the takeoff angle is perpendicular to the orientation of the antenna- so, if the antenna is vertical, you’ll have a very shallow takeoff angle, aka groundwave, if its horizontal, the radiation goes vertical. NVIS generally works best between 1.8-8mHz, with the higher frequencies working better during the day and the lower ones at night.
I’ll also add to this that the direction finding threat almost exclusively comes from groundwave. So on HF, NVIS is what you’re looking for. As little groundwave as possible.
So with that said, let’s talk about this antenna.
The first thing to know is that its built out of dirt cheap materials. 128ft 14AWG stranded wire, a Cobra Head, and ten plastic electric fence posts. Less than $25 or so.
For an 80M dipole antenna, each leg is going to be roughly 64ft long. You can make a loop or use a ring terminal to secure the wire to each end of the cobra head. Stretch it out- now you’ve got a dipole. Those plastic fence posts serve both as a suspension for the antenna and as an insulator. All you have to do is wrap the ends in a loop, and boom, you’re ready to rock and roll.
The antenna itself is roughly 2ft off the ground. This creates a high amount of reflectivity from the ground, sending your radiation almost completely vertical.
And with that, you’ve got a dirt cheap antenna that works pretty well. If you want to see how it works and get hands on building one, come out to class.

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By Published On: January 21, 2021Categories: Comms, NC Scout66 Comments on Training Notes: HF NVIS Antennas

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About the Author: NC Scout

NC Scout is the nom de guerre of a former Infantry Scout and Sergeant in one of the Army’s best Reconnaissance Units. He has combat tours in both Iraq and Afghanistan. He teaches a series of courses focusing on small unit skills rarely if ever taught anywhere else in the prepping and survival field, including his RTO Course which focuses on small unit communications. In his free time he is an avid hunter, bushcrafter, writer, long range shooter, prepper, amateur radio operator and Libertarian activist. He can be contacted at [email protected] or via his blog at brushbeater.wordpress.com .

66 Comments

  1. Matt January 21, 2021 at 07:37

    Would a reflector wire, laying on the ground underneath, make any difference in efficiency?
    Matt

    • NC Scout January 21, 2021 at 08:09

      It does if you’ve got poor soil reflectivity. Since we’ve got a lot of silica here, it’s not an issue.

    • Keypounder January 21, 2021 at 18:53

      reflector wires make a difference in gain over poor conductivity soil, as NC Scout says, but they also can affect the impedance of the antenna and make it easier to get a really good match. They reduce the effective soil depth, which is why you get more gain, and that also can make for a better match. If you are going to do that, I’d suggest putting three down, about 5′ apart, each about 5% longer than the antenna. If you want to get really hardcore cause you have really bad (or no) soil, buy a 4′ wide 150′ roll of chicken wire, cut it in half, and lay that under the antenna, soldering the two pieces together every foot or so with new plumbers solder. Cover that with rocks and let the weeds grow over it this spring. The RSGB antenna books talk about doing that; haven’t tried it yet. If you go for a Vee configuration and are want a better match, you don’t need a tuner, just raise or lower the antenna till you get the impedance you want. I’ve seen low dipoles with impedances from 25 to 100 ohms- change the height and see what happens.

  2. Tator January 21, 2021 at 07:42

    Good stuff. After studying for pretty near 50 years I went and took my tech and general. Figures like everything else I have done, the gov is likely fixing to break our chops over it, which is why I never did it before. I took that class that was posted I while back down there where you are, and a couple others that were posted online for the general. Wish I could find one for the extra, but because of the recent questions change not any good ones out there yet.
    Ordered a bunch of them cobra heads from china back when we talked about them last, and not sure they are even going to show up. So broke down and paid 2x more money from amazon. Least I have a couple now with the adapters (don’t forget them unless you plan on using BNC connections straight through).

    • StormN January 21, 2021 at 12:29

      If you’re looking to study for Extra I can’t recommend HamStudy.Org enough. For Tech and General I liked using its flashcard method.

      • Tator January 21, 2021 at 16:47

        Yeah, I paid for it to have it on android. Have a couple other apps and a kindle book too, as well a hardback book. I really like video format though. Easier on the eyes than trying to read, plus I like the expanded theory some of the videos offered. Thanks for the recommendation though.

        • StormN January 21, 2021 at 18:36

          I used it on my laptop/desktop. I didn’t immediately figure it out but on the HamStudy.org ‘flash card’ method if you click on a marked corner it ‘flips’ the card and shows an explanation or theory plus links to more vetted sources of more info! It seems a bit of a secret or hidden but I think for good reason: I’ve been told time and again that to prepare for the license tests you DO NOT want to try and understand – just study for the answers. I’ll wager you know and likely agree on this point. Understanding can come later. I’m reading that learning CW has a somewhat similar counter-intuitive stumbling block.

  3. B hi January 21, 2021 at 08:09

    Very cool.

    • StormN January 21, 2021 at 12:30

      Agreed. Thanks very much!

  4. deanqq January 21, 2021 at 08:43

    It works that low to the ground? I’ve always tried to keep mine 6-10 feet high (not easy in deserts). Never occurred to try that low! (we know what ASSume means). Dang. Now I have to drop every thing and go try.

    • NC Scout January 21, 2021 at 08:47

      Works great.

  5. J J January 21, 2021 at 08:53

    What would be a good starting HF rig? I’m studying for General license and looking at re-learning CW.

    • Keypounder January 21, 2021 at 10:32

      HF rigs. Well. Easy question, complicated answer.
      First question is- what is your budget?
      Second question is- New or used?
      Third question is- do you want DC to daylight or just HF?
      If the answer to 1) is “cheap as possible” 2) is ‘new’ and 3) is just HF, then the IC718 at just over $500 is an option.
      If your new HF radio budget rises to $1200, then I’d take a look at the IC 7300 or the Kenwood TS590SG. These both have HF and 6 meters, and both are VERY good radios.
      If you want DC to daylight (HF +VHF +UHF) then the Icom 7100 or the Yaesu Ft991 are options.
      If you want used and want to spend less than $500 and are capable of radio repair then there are LOTS of options. I’d try to find someone who wants to get rid of their IC7200. If you can get that for under $600 you got a bargain. It isn’t light, but it was designed for portable operation.
      I would echo NC Scout’s advice and AVOID QRP radios, at least while you are learning.
      I would avoid anything more expensive than that until you have a couple years of operating under your belt, and at that point you won’t need to ask anyone else what you want, you’ll know.
      Keypounder

    • Jon January 21, 2021 at 10:43

      JJ
      Scout covered this in the last episode of AP Radio. Link is on AP main page.
      I bought an ICOM 7200. It’s super simple to set up and operate. It’s also a hardware radio, not a software designed radio like the 7300.
      I would stick with a base station radio for a first rig. ICOM, Yaesu, Kenwood all have good entry level radios for around $1K, give or take. DXengineering, Giga Parts, and Ham Radio Outlet all all good sources I’ve used.
      The mobiles are OK too, but more complicated menus to learn because of the smaller form factor. Everything is a trade off.
      You could save a few bucks buying used from a club near you. I would hesitate to buy used over the net because you don’t get to test before you buy.
      YMMV

    • StormN January 21, 2021 at 12:34

      I vote for Yaesu FT-891.

  6. Jon January 21, 2021 at 09:13

    Once upon a time a fellow used electric fence wire because that’s what he had leftover from fencing. No one notices an extra strand of fence wire out in America. Seems to work fine if you make sure to weather proof the cobra head because electric fence wire is coated steel. It will oxidize much worse than stranded copper.
    Theoretically there’s some reflectivity and inductance from the metal fence posts and adjacent wires. It’s nothing that my inexpensive LDG tuner can’t handle.
    This radio stuff isn’t as hard as some people make out.
    Anyone have experience with that cheap Chinese G90 SDR? On paper it looks good for portable because of the low power consumption. And it’s easier to fit in a family budget that a KX3.

    • Keypounder January 21, 2021 at 10:10

      Aluminum electric fence wire works pretty well too; if you use No-Ox and coat the connection to the ring terminals with liquid tape, galvanic corrosion is less of a problem

    • StormN January 21, 2021 at 12:37

      “This radio stuff isn’t as hard as some people make out.” Easy for you to say:)

      • Jon January 21, 2021 at 15:03

        StormN
        Once upon a time I was filled with trepidation about lots of things, radio among them. Getting some training was useful for two main reasons. First, I gained enough knowledge to operate the gear safely. Second and most importantly is confidence building that comes with competence. Confidence that I’m unlikely to wreck a radio if I follow a reasonable set up protocol and avoid wild swings in reflected power from non-resonant antenna.
        The hardest part of any journey is the first step. For most things, just start within your capability and risk tolerance. Supplement training and education as you learn. The tools are more useful as you gain experience. That applies to cars, radios, guns, chainsaws,…most things a man might need.
        With commo stuff I’m at the consciously competent level. I still have to think about technical stuff like Max useable frequency, grey line impacts, etc, for HF. Practice and study have been helpful. I’m still a novice on digital. I can use FLDIGI on a laptop. Need to get a headless PI working properly for portable.
        The ARRL books are really quite good on the basics and theory. They’re probably at your local library. Worth getting the general study guide as a reference.
        Like shooting, it gets easier once you get past the initial excitement.

        • StormN January 21, 2021 at 15:14

          Thanks!

    • Cavguy January 25, 2021 at 11:09

      Hey John, there are good deals on used equipment out there. I recently picked up a very fine KX2 for SOTA activations. Went to QRP Guys for antenna kit, and a supplier for some kite wire. All for less than $650. Please try to avoid giving ANY money to the Chinese.

  7. Keypounder January 21, 2021 at 09:59

    For those interested in more information, you can go to the BrushBeater site and look up NC Scouts intro to NVIS and my 3-part article on NVIS. Here is a link to the first- https://brushbeater.org/2016/08/15/nvis-explained-i/
    That series drew upon a variety of sources, including Fiedler’s work and Patricia Gibbons WA6UBE (SK). I had thought her old website was gone, but the wayback machine has some of her stuff preserved-
    http://web.archive.org/web/20131208150417/http://www.tactical-link.com/field_deployed_nvis.htm
    I’ve done this with as few as 5 posts, one at each end, one in the middle of each leg, and one at the feedpoint, and if you apply tension to the ends it works fine. In a cleared area the posts are good, but if you have trees conveniently located, you can attach the ends at 6 or 7 feet and let the antenna hang with the feedpoint at 3 feet, give or take and it works fine.
    Take a look at the graphs in that series for some idea of relative signal strength based on height; as NC Scout notes, a lot depends on ground conditions. The FCC has a regional chart that gives a reasonable idea of average ground conditions across the USA. https://www.rfcafe.com/references/electrical/images2/fcc-ground-conductivity-map-1975.gif Note that the
    NOTE: local conditions vary widely, especially in urban and suburban areas, and mountainous areas. Also note that the physical top of ground does not necessarily correspond with the RF reflective layer, especially as the frequency drops.

    • MortarGuy January 21, 2021 at 14:52

      Great articles and resources, thank you. I’ve learned so much over the last months from reading the articles and resources linked. My question is about that FCC map – is a lower or a higher number better for NVIS propagation? Thanks again, AP. You guys are great!

      • NC Scout January 21, 2021 at 15:14

        Lower- lower the frequency, the better.

      • Keypounder January 21, 2021 at 19:23

        @MortarGuy
        Propagation relates to the ionosphere. As NC Scout noted, NVIS *propagation* is better at lower frequencies; IOW you get more hours in the day in which NVIS works the lower the frequncy. This map is about ground conductivity, and while ionospheric currents and activity are apparently somewhat related to ground conductivity, I think what you were asking was how conductivity impacts NVIS *operation*
        So, the lower the number, the lower the area AVERAGE soil conductivity. This means more loss. For NVIS, more conductivity means you can keep the antenna lower down and get the same vertical gain as somebody with less conductive soil; I touched on that in my article. It also means that vertical polarization, meaning ground wave, gets attenuated LESS, making it easier to DF you. Lower conductivity = More attenuation which means lower chance of DF, less noise, less low angle radiation.
        An amateur operator would probably prefer more conductive soil. A clandestine operator would probably prefer less conductive soil. Most of the time, you use what soil exists where you are operating and won’t get to pick. Keep in mind, too, that these are area average values and there will be WIDE local variation.
        Either way, raise or lower the antenna until you get where you want to go. The lower the antenna, the less gain *and* the less noise. Unless you are over a salt marsh. Finding the sweet spot for your particular location is why this is an art, and requires practice.
        Keypounder

        • MortarGuy January 22, 2021 at 02:10

          Thank you for the informative reply, Keypounder. NC Scout answered the question I didn’t ask, you answered the one I did, clarified my ignorant verbiage, and added some excellent points. Thank you both for your time and patience. Comms is a fascinating art and I hope to gain a solid working knowledge as time goes on.
          73

          • Keypounder January 22, 2021 at 08:43

            @MortarGuy:
            You are welcome. We are all students, MortarGuy; some of us may be studying at a different level. I have no doubt that there are many things I could learn from you; but this is a topic I’ve studied for awhile.
            Keypounder

  8. Johnny Paratrooper January 21, 2021 at 11:29

    Does this have anything to do with that?
    This is a cool video.
    https://www.youtube.com/watch?v=hJDl4dUlFiI

    • NC Scout January 21, 2021 at 15:17

      That just looks like a waste of tax money.

      • Johnny Paratrooper January 21, 2021 at 16:57

        Roger. I thought ya’ll were using this to bounce signals or something.
        I wondered because this would work both ways since you don’t control the infrastructure.

  9. Tim January 21, 2021 at 11:47

    Can a 2nd 40 meter antenna be strung underneath or on top of the 80 meter antenna using the same plastic fence posts or would that screw up propagation? If that is workable one could have a dual band antenna.

    • Jon January 21, 2021 at 13:23

      Tim
      You can indeed stack antennas for multi band operation. That’s precisely how fan dipoles are built.
      The resonant lengths of stacked antennas tend to be a little shorter than theoretical lengths. That’s ok. Soil conditions and height above ground also impact the resonant lengths some. It’s nothing to worry about if you’re using a decent antenna tuner.
      To avoid a phasing problem between the antennas you’ll probably want to use a single feed point for both antennas. Easy enough with the rough and ready cobra head technique.
      The purists might fixate on disruptions of propagation lobes or takeoff angles from multiple conductors. All that stuff is negligible for NVIS single channel communication at HF. Don’t worry about it.
      Build your antenna and get to work. Try not to over think it. (Lord knows that I’ve been guilty of trying to get perfect at the expense of good enough)

      • StormN January 21, 2021 at 14:56

        I’ve been thinking about making a ‘buddy stick’ for multi-band use like in this video. It sounds real good and relatively easy for me. Any thoughts would be appreciated.
        https://www.youtube.com/watch?v=E8JrZxPkCLs

        • NC Scout January 21, 2021 at 15:15

          You could, but the buddy poles (or ham sticks) are almost always erected vertically.

        • Jon January 21, 2021 at 15:36

          StormN
          HamSticks can be used in horizontal polarization configuration. We used them that way when I lived in VA. Portable and quick to put up at a mobile EOC.
          THat said, i much prefer budget friendly wire antenna for HF out in America. In cities or subdivisions with limited space, the HamStick or loop antenna become a better option.
          Last time I lived in a subdivision I used a random length slope antenna with a 9:1 DIY balun. It worked ok on 20 and 40meters. Lower frequencies were hard for the tuner to match. Main point is that a wire antenna can work almost anywhere and they’re cheap to experiment with.

  10. Hank January 21, 2021 at 15:51

    I have a G90, awesome tuner everything else works ok. FLRig has it in the database and it works. Good signal reports. Digital takes some tweaking to get sound levels right. Lots of help at xiegug90.groups.io
    The internals are robust, but it is a Chinese radio. I have never used anything else so no comparisons.

    • Jon January 21, 2021 at 16:33

      Hank
      Thanks for your report. Useful info to have a first hand user report.
      Is the current draw near the advertised value?
      How does the visual band scope work for finding in band signals?
      This radio seems like the budget option of choice right now for portable operations. Especially since it has an internal tuner.

      • Hank January 23, 2021 at 11:02

        The current draw at transmit is less than advertised on TX the max I have seen is <6 amps, RX runs about .6. I find the bandscope very helpful. I bought it because of the internal tuner and the price, I would buy it again. If you buy one join the G90 group on.io, lots of good info and help especially on how to set the rf gain and use the ALC. The radio can be modified to open up TX freqs also. Again I have no experience with other brands so YMMV.

        • Jon January 23, 2021 at 12:39

          Hank
          Thanks so much for sharing the details on the radio. Very helpful. It’s looking more and more to be a sound investment for portable HF!

  11. HighCountry January 21, 2021 at 17:36

    I have used NVIS in supporting a Running Race that goes up a twisting up a canyon with several thousand feet of granite walls on both side of the road. We could communicate very well between the 9 miles of granite using NVIS.
    As far as I can tell, there is only one book that is a dedicated NVIS book and it is only available from DX Engineering.
    Near Vertical Incident Skywave Communication
    Theory, Techniques, and Validation
    by, LTC David M. Fiedier and LTC Edward J Farmer
    I especially liked the picture of Erwin Rommel’s command Vehicle with loop antenna on the top
    Heinz Guderian said “I want to command over the radio from the front, not talk about it in the rear on a telephone”. He had originally commissioned a signal officer before developing the “Blitzkrieg” doctrine.
    The book is very good, with much of it above my pay grade. But there are lots of photos and diagrams.

    • NC Scout January 21, 2021 at 18:18

      I’ve got the pdf to download it on Brushbeater.

  12. Keypounder January 22, 2021 at 08:57

    As I mentioned in my NVIS article, it is possible to use a dipole just like the one mentioned in this post as a tool to measure the actual ground conditions at your particular location. There are other ways to do that as well, and if you are interested, see N6LF’s link — https://www.antennasbyn6lf.com/measurement_of_soil_characteristics/
    Keypounder

  13. James January 22, 2021 at 17:30

    OK folks,a off the article radio ?.I am working in a old home,120,years or so.The beams in the cellar are old trees just debarked,not cut.
    Anyhow ,tacked all along these old beams are many old 60+ years in some cases,ham radio licenses from clubs around the state(this is a job in Mass.)with call names and such.They are still together but getting beat up and was wondering is there a ham radio museum ect. that might be interested in them,the owner if I can find a home for them is cool with this.
    I will also reach out to local clubs in the area and see if they have any ideas,feel history of this may rot away as time moves on,not even sure if this house will remain standing or be knocked down for a new home.
    Though no visible signs of antenna attachment. to home feel must have been a ham radio group of some nature from many different towns/cities.

  14. Matt January 22, 2021 at 20:05

    This is a great article, and the comments kick it up another notch. But I gotta ask because I see this a lot here – how can there be 42 comments (as of my typing this) and yet not a single person has rated this article with “the stars”? Seems odd.
    We could probably help others by showing them the best articles via our ratings. I’ll be the geek and give it a rating.
    Matt

    • StormN January 23, 2021 at 03:43

      Doh! I hadn’t noticed about the stars! I’ll wager most others haven’t either. Good catch!

  15. Anonymous January 22, 2021 at 20:05

    5

  16. Anonymous January 23, 2021 at 13:20

    4.5

  17. […] saw the new NVIS Ant article – looks interesting – I’ll have to try that (smirk!). Some notes on it – Any horizontal ant within […]

  18. Anonymous January 24, 2021 at 07:07

    1

  19. Anonymous January 25, 2021 at 08:57

    0.5

  20. Homer January 26, 2021 at 21:21

    I’m guess a balun will be needed with the coax correct?

    • NC Scout January 26, 2021 at 21:22

      No. Just run it with a cobra head.

    • Jon January 26, 2021 at 21:40

      Homer
      A Balun or UnUn is an impedance matching transformer to balance antenna system with the 50 ohm impedance your radio front end expects to see. It’s not needed so long as your antenna is close to resonant on the frequencies of interest. Any decent tuner can take up the slack and get a match.
      With coax you might want to insert a choke in the transmission line to eliminate unbalanced current that can cause RF at the radio and prevent a nasty shock. Good station grounding goes a long way to eliminating it.
      There are tons of RF choke designs from simple air coils (that may not always work all that well) to ferrite coils or ferrite beads on the coax.
      As a general rule, I use ferrite beads on the outside of the coax feed line. It doesn’t do any harm and might do some good. They’re cheap enough and easy to use. A 1:1 balun accomplishes the same thing, but it’s a lot bulkier, so I just go with the beads.
      You can also use a 1:1 balun in place of the cobra head to build your antenna in a more permanent installation. It’s just bigger and heavier, and those are not helpful for portable operations.
      Scout has provided a great way of getting started on HF without spending a ton of cash. It will work just fine. I use a similar set up for portable HF. My shack NVIS antenna is only slightly different because it’s a semi permanent installation.
      Experiment and enjoy!

      • Homer January 27, 2021 at 21:38

        So a balun/unun is only needed for non resonant antennas such as ocfd and end fed antennas then? That simplifies things alot. I had always thought a balun was needed on dipoles because the antenna is electrically balanced but the coax is not. Thank you

        • Keypounder January 28, 2021 at 13:51

          @Homer:
          You want to minimize rf on the outer shield of the coax getting EITHER to the radio, or to the antenna. For NVIS antennas like this one, as NC Scout notes with the coax lying on the ground the ground itself acts as a choke. Where possible, route the transmission line away from feedpoint perpendicular to the antenna, keeping it *on the ground.* These temporary installations, with short feedlines typically on or even under the ground, usually do not require a balun.
          BUT. Even a hundred watts can cause issues with RF at the operating position, especially since many portable setups lack a good ground at the OP. A aluminum tent stake in the ground is better than nothing, especially if you wet the ground around it with conductive solution (urine, epsom salts, ice melt or rock salt,) but may not be adequate, depending on the ground and on how well balanced the antenna *installation* is. A dipole cut to exactly the right length, erected to uniform height above a perfectly uniform ground, with no trees or obstacles within the Fresnel zone and the feedline routed perpendicularly away from the antenna for a wavelength or more, does not need a balun. In the real world almost all antennas are imbalanced to some extent, and have common mode currents to some extent. The higher above ground the antenna, and the more cables you have connected to your radio, the more likely it is that common mode effects will become objectionable. For my Field Day setups, I employ chokes at the feedpoint and the radio, as well as clampon chokes on the cables to the keyer, microphone, and computer from the radios, and a driven 4′ ground rod at each OP, and I sometimes still have RF issues.
          Higher antennas can benefit from a choke balun, and I routinely install a homebrewed toroidal choke balun as the feedpoint on all my coax-fed antennas, and close to the shack in longer feedlines. I use these because they provide the maximum choking resistance for the least money; ones rated up to 700 watts or so I make for under $20 each. Smaller ones for power levels 100 watts and under are cheaper and lighter still.
          The reason I use single toroids is that choking impedance rises as the square of the number of turns; beads on a coax line provide, say, 15 to 50 ohms of impedance, give or take, for each bead depending on size, shape, material and frequency. 20 beads might give you, say, 500 ohms impedance. Jim Brown, K9YC, recommends much more impedance than that for best performance, especially on the low bands; see http://www.k9yc.com/RFI-Ham.pdf for the details.
          The W2DU-type baluns are a string of small beads on a piece of small coax coiled up and stuffed in a tube. They typically provide 500-1000 ohms impedance, depending on frequency. The reason that some of the beads get hot is because even that level of impedance does not stop the induced common mode, and the first beads in line absorb the heat from that current. The bifilar wound choke balun K9YC recommends is cheaper, more robust, and uses only one toroid for most applications; the balance of the material required is commonly available stuff, no $3 per foot coax, etc.
          For temporary NVIS setups with very low antennas, choke baluns are NOT required, but do not make the mistake of generalizing this to saying that choke baluns are never a good idea. In fact, the reverse is true; a choke balun is usually a good idea EXCEPT under special circumstances, and especially so if you are going to employ digital communications, with a tablet or laptop connected to your transceiver.

          • Jon January 28, 2021 at 15:36

            Keypounder
            That’s a superbly written point on managing common mode differential current and managing RF at the operating station. Quite well done. Thanks for posting it for the benefit of all.
            Ferrite beads are OK for shunting common mode currents. Torroid wound inductance coils are better. I use the bead type chokes for portable and field day. Torroids are in use at the main station.
            Thanks again for taking the time to write so clearly and help everyone out.

          • NC Scout January 28, 2021 at 16:54

            These comments are why I love doing this!

          • Jon January 28, 2021 at 17:21

            Keypounder
            Can we shift topics and discuss front end protection for near field stations? Maybe a separate post?
            Scenario: field station transceiver TX and RX on 40m HF, common uniden or whistler scanner montoring VHF and UHF frequencies of interest, SDR receiver fed by a beverage type antenna scanning 40 and 80m, 50W VHF mobile transceiver for both TX and RX in shack. Operators transmitting on both HF and VHF. How to protect scanner and SDR from near field overload without using commercial TX/RX antenna auto switches?
            I’m personally struggling with this problem. Simple in line diode attenuation doesn’t work well because it dampens all incoming signal.
            Standing by.

          • Keypounder January 28, 2021 at 18:16

            @Jon:
            The answer is bandpass filters.
            My crew and I have run 3A on Field Day with 80,40, 20 and the VHF/UHF bonus station and the only trouble I had was with 7th harmonics on the 40 meter station impacting the 6 meter operation, and it was not a big problem; putting another stub in the 40 meter bucket cut for the bottom end of 6 meters would do it. These operating positions were quite close to one another and the antennas were all within 100 yards of each other.
            I have a set of ‘bandpass buckets’ that include both the W3NQN style bandpass filters AND tuned coax stubs for each band from 80 to 10 meters.
            With a good transceiver and good coax stubs you can even run either end of the same band; look at the Sherwood Engineering evaluations of receiver capability- http://www.sherweng.com/table.html
            ANYTHING on the first two pages would be an excellent choice. I’ve compared the K3 and the KX3 with the TS-590SG and can just barely tell the difference, and the Kenwood is significantly less expensive. As much as I like the IC-7200, for a wealth of reasons, it isn’t in the same league as the Kenwood. Same with lower end Yaesu rigs and I’ve used a number of them. If you are going to run a multi-station setup while sharing bands, then you must have a radio that provides the isolation required. the problem is that most of these rigs are so expensive, big and heavy that they don’t suit a field portable operation. The Kenwood isn’t light, but is compact and rugged.
            regards, Keypounder

          • NC Scout January 28, 2021 at 18:33

            If we can, let’s get this written up as a post. That way people will be able to download and save it as a PDF. This is THAT good and it deserves it.

          • Keypounder January 28, 2021 at 18:54

            @El Jefe Maximo AKA NC Scout-
            so let it be written, so let it be done. The Scout has spoken.

  21. Jon January 28, 2021 at 20:16

    Keypounder
    We’ve run out of reply space on the stub thread 😉
    This is a bit of a Doh! Moment for me! I hadn’t even thought of tuning stubs. I was too target fixated looking and signal processing between the feed line and the receiver. Now I’m going to have to go study a bit and rethink configuration.
    I run a high pass filter on HF to reject strong commercial
    Signals. Now I will need to study a bit to make up a notch filter focused on the public service bands so I can protect scanners. Since it’s cold outside I will have time to work on it. Sadly, I don’t have a scope to do detailed circuit response testing. Field expedient means will have to do.
    The IC-7200 is my HF rig. I agree that receiver sensitivity and selectivity leave something to be desired. It still better than the yaesu mobile that it replaced. Good radio for me and simple to operate. That’s a bonus. I will have a look at Kenwood tho. You never know what will pop up on the used market.
    Thanks again for pointing out a viable solution. Exceptionally helpful.

  22. John July 30, 2021 at 09:29

    I am switching to 1X7 copper fishing leader for the elements, coiled into 2 chalk line reels to expedite deployment and teardown, save space, and save weight. Waiting on the mailman, but i should be able to get an 80m dipole at max extension, and retract as needed for tuning higher frequencies. Also ditching the goat fence posts and going to 3 aluminum telescoping tarp masts. 1.1 pounds each. I AM using an LDG 1:1 current balun as the feedpoint. I understand what you are saying about the coax being choked on the ground, but my goal with this setup is maximum versatility and the ability to ditch my tuner for backpack use. I might want to set it up as a vertical to contact a further operator at some point. This is all an experiment and may or may not work in the long term, but for the $130 investment I figured it was worth exploring.

  23. NC Scout August 11, 2021 at 16:58

    5

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