The Poynting Vector Antenna

Radio amateurs are inventive people, and though not all of them choose to follow it there is a healthy culture of buildng radio equipment among them. In particular the field of antennas is where you’ll find a lot of their work, because the barrier to entry can be as low as the cost of a reel of wire.

Over the years a number of innovative antenna designs have come from radio amateurs’ experimentation, and it’s one of the more recent we’d like to share with you today following a [Southgate ARC] story about a book describing its theory (Here’s an Amazon link to the book itself). The Poynting Vector antenna has been one of those novel designs on the fringes for a while now, it has been variously described as the “Super-T”, or the “flute”. Its party piece is tiny dimensions, a fraction of the size of a conventional dipole, and it achieves that by the interaction between a magnetic field across the plates of a capacitor in a tuned circuit and the electric field between a very short pair of dipole radiators. The trade-off is that it has an extremely high Q and thus a narrow bandwidth, and since its feeder can become part of its resonant circuit it is notoriously difficult to match to a transmitter. [Alan MacDonald, VE3TET] and [Paul Birke, VE3PVB] have a detailed page on the development of their Poynting antenna which takes the reader through the details of its theory and the development of their practical version.

In the roof space above the room in which this is being written there hangs a traditional dipole for the 20m amateur band. Though it is a very effective antenna given that it is made from a couple of pieces of wire and a ferrite core it takes most of the length of the space, and as we’re sure Hackaday readers with callsigns will agree a relatively tiny alternative is always very welcome.

If antennas are a mystery to you then we’d suggest you read an introduction to antenna basics to get you started.

44 thoughts on “The Poynting Vector Antenna

  1. -12 dbd gain is awful an makes not credible that “we could still copy *all* the weak signals heard on the dipole”. In this context only signals below -91dbm should have been checked.
    -4db on the noise floor is simply not enough to offset the remaining -8db in the equation.

    12 db is the kind of gain you get with a 5 elements yagi vs. a dipole: why go to such lengths if so neglectable.

    Then, if we’re just talking “anything that can get you on the air”, a comparison with a similar sized piece of wire coupled using an “antenna tuner” shall be made.
    My bet is on rather similar performance.


  2. I’m sorry Jenny but I have to ask, was this article proofread before it was posted?




    Spelling errors (buildng?), lack of commas, run on sentences? Everybody makes errors now and again but these should have been easily caught before publication.

    1. Why thank you for your feedback, and have a Gold Star for spotting a typo. They happen, life moves on.

      Long sentences, economy of commas? Years working for the dictionary gave me a training in putting words into order from some of the finest in the business, but it didn’t blunt my ability to spot a troll. :)

        1. Please everyone. These people running hackaday are hackers. If they were writers they would not be here.
          I am not a writer I am a hacker. my writing would be shit on here.
          Thank you and please keep this in mind.


          1. I’m nor writer or hacker, but as a foreign language native I’d like to read correct and understandable sentences to get the essence of it.
            BTW: I’m radio amateur.

          2. When you write for money you are a writer. You are selling your writing with the understanding that it will be clear, interesting, and topical.
            If you find errors/typos you can be condescending, simply point out that there are errors/typos,or horror of horrors: let the typos go. The choice is yours.

            Choose wisely.

      1. I am not sure it’s fair to lobby trolling accusations when my observations are factual. You also fail to correct any of the issues raised but instead lob accusatory statements at me instead of just addressing the underlying issues in your article.

        Years working for a dictionary should easily assist you in determining that your post still uses the incorrectly spelled word “buildng”, which should have been caught and corrected or simply proofread to begin with by yourself or an editor or corrected when pointed out. Any writing program, including your browser, should also highlight that minor mistake as incorrect so it can be easily spotted and corrected prior to publication.

        The misspelled word alone wasn’t the major issue here because mistakes do happen. The bigger issue is the way the entire article is written that stands out as run on sentences, disjointed phrases and is just awkwardly phrased in several spots. It hurts the conveyance of your message and comes across as unprofessional. That’s all. Nothing personal against you, I just cringed several times when trying to read this article and finally had to say something because I cannot be the only one who notices this and it feels like it should at least be pointed out so it can hopefully be addressed in future articles.

      2. @Jenny List – Being a quasi-logarrhea victim myself, I feel your pain. :-)

        However, we dyed-in-the-wool technologists here at HaD are less worried about syntax and grammar like some anal-retentive English teacher would be. We are more concerned about the technology content. I find that most of your articles are interesting and very readable. It appears that only a egotistical misogynist would take exception to your report writing skills.

        In this article I believe you nailed it. It was topical, detailed, and contained new concepts to most of us. I’ve seen US Navy (SPAWAR) articles that had an idea to resonant a stream of sea-water squirting out of a nozzle vertically on the side of an US Aircraft Carrier or other military ship. They control RF bandwidth with stream height regulation. It was just invented approximately 7 years ago and may go into full operation soon. Your article is on par with that. Bravo!

        Furthermore, when someone uses a emoticon like :) it seems that the intended recipient never understands the tongue-in-cheek reference that precedes it. Some people need to chill out and check their HUGE ego at the door. I know what you meant and also benignly smiled too.

        1. I take issue with your misogynistic allegations. Sorry but none of my concerns have anything to do with Jenny’s gender and nobody brought gender into this discussion to begin with until you did. I agree with you that content should be meaty and informative, my issue was that reading through it was difficult due to multiple basic errors in grammar and spelling that should have been proofread by the author and the editor(s) prior to publication. Especially for somebody whose self reported primary job qualification was working for a dictionary. It would be like going to a restaurant and finding that the food was not being refrigerated prior to being prepared or basic hygiene standards were not being met.

          This is a site that has physical value, sells advertising, cultivates a community, bills itself as a professional operation and this is far from the first time this has happened with this writer specifically. I actually didn’t even notice who wrote the article until I finished reading it but was not surprised to learn who the writer was, because several other articles they have written have been similarly problematic. It keeps happening. To be fair, at the end of the day, the readability is a minor point overall because clearly one can still absorb the basic information of the article but it is unprofessional and should have been reviewed prior to publication such that it was never an issue to begin with. The only issue I raised here was my concerns about the writing quality and only felt the need to do so because it was bad enough in this case and the author’s response of basically saying “screw the readers, we all make mistakes, deal with it, smiley face” keeps happening and is unprofessional.

          I try to contribute to this site fairly regularly, providing helpful followup, related links, information that is relevant to the topic at hand and that contribution is not isolated to only positive things. If there should be improvements to the site or the people writing for the site that would benefit all of the readers, that isn’t some kind of sacred thing that should never be mentioned. That does everyone a disservice.

          Asking for basic journalism, proofreading and editing from a site so that everybody can benefit from it is the opposite of being self-centered. It’s asking for the author and the editors to act responsibly and professionally such that all of the readers are able to clearly and easily read the content without having to stop every few sentences to try to ensure they read or understood things correctly because of fundamental problems with the grammar, sentence structure or spelling.

          1. How can you take issue with an alleged allegation when the alleged alleger never once used your moniker or screename? You appear to be very sensitive to what you assume is criticism. I agree with you that journalists should use spell-checkers and thesaurus for their articles. However, mistakes happen. Jenny has earned here bona-fides, street-creds, made her bones, etc. She is a very smart women who make many of us males pale in comparison.

            She is also very Yank-knowledgeable. That is a big plus with us Yanks that look up to such things. It’s funny to us Yanks when we see Brits trying to imitate us and analyze our culture and get it wrong. Jenny is quite aware of our culture and “gets us”. We don’t get all twisted because a journalist forgets to put an “i” in building and others. It’s no big deal. Yes she should correct it but not on your timetable. Brian usually corrects this stuff by default anyway.

            So in a nutshell I’m saying there’s a HaD way of doing what you did. We don’t write 2-3 paragraphs lambasting the writer for grammatical errors. We just use one pithy sentence making a tongue in cheek wise crack about it. The writer (or Brian) usually fixes it ASAP. I’m not saying your wrong, but why slam Jenny over something the rest of us could not give 2-craps about anyway. It’s a NO BIGGY! She pointed out this cool mostly undocumented antenna and we’re intrigued. The rest of us, including the HaD corporate backers, could care less.

            BTW to our other international friends who don’t quite understand western emoticons, colon and a letter P or :P is not what you think it means. It’s not a common term of endearment like a smiley face or :-) it’s more like a term of mild ridicule or a terse mocking response to something we did not like. It is supposed to be a person sticking out their tongue like a child does. That’s at least an American expression of derision not friendliness.

            That last paragraph was a sideline comment so don’t respond to it as it was not aimed at you. However, the following is: The emoticon used after using the word “troll”, was NOT an accusation that you were a troll. She was just being humorous or otherwise not seriously intentional, and it should not be taken at face value. She may have been implying that it was TROLL-like however. She just took umbrage to your use of multi-paragraphs to correct a simple faux pas she may have made and overlooking the intriguing content, which you must admit you did do.

            Bon travail – Jenny!

    1. I’m wondering how hard it’d be to use one of the GPIOs on a lot of them to control a servo of some kind to vary the tuning capacitor automatically too. It’d be really interesting to try.

      1. Although the book is relative new the authors and the idea is some years older. Plus, it seems to be very theoretical.
        An up-to-date hacker would use a tuning circuit with Arduino and motors for sure.

    2. The high Q implies low bandwidth, which means it would essentially be a great pre-selector for any radio that has to deal with local strong interfering signals.

      It might not be as useful for SDRs, though. The low bandwidth would limit the usefulness of ‘waterfall’ displays which show activity over a section of the band. I don’t know what bandwidth is claimed for this antenna type, but efficient magnetic loop antennas (another type of compact, high-Q HF antenna) can have a bandwidth as low as 4-10kHz. This is very small compared to the normal bandwidth available to the waterfall display and it would be like looking at the band spectrum through a keyhole.

      1. Just do like they suggest in the video and use multiple streams. You can even scan each one over a range of frequencies by varying the pressure. And maybe rotate which antenna is on which band in real time. The end result would be a functional waterfall display for your ‘waterfall’ display. Just imagine the scanning capabilities of a couple truck loads of road salt in the Bellagio fountain. XD

  3. Oh no, not again! The quest for an electrically small antenna has gone on for decades. Numerous charlatans and well-meaning enthusiasts have built small, highly tuned things and claimed excellent performance on ham QSOs. Variously, the Crossed Field Antenna, the EH antenna, and the one that landed on my dessk a decade ago, the Radio Photon Antenna. They are all radio snake oil, and generally perform because they tune up the feeder!

    Please, please, don’t ever be tempted to buy one.

    1. I wouldn’t buy one, but I might make one if I had the time.

      But yes, there is always a catch somewhere. Take the magnetic loop as an example, it’s small and effective, but the catch is narrow bandwidth and huge induced voltages.

  4. EH Antennas, Crossed Field Antennas, Poynting Vector Antennas, similar theories come back around every few years, making extraordinary claims about “big” antennas in small spaces, seemingly defying physics, or exploiting some as-yet-unexplored phenomena. Sometimes someone has a product to sell, that some swear is worth its weight in gold, and others consider to be an overpriced “dummy load”, I think it’s fair to say many have been burned by products that don’t live up to the hype. Other times there’s no product, but a lot of experimentation with all sorts of mixed results varying from mundane to “WOW”. Obviously we would (or SHOULD) all leap at the chance to help unearth some new untapped physics, but in the meantime it’s hard to tell if this is all real science, or pseudo-scientific voodoo. The authors themselves admit that it’s extremely hard to tune/tame these antennas and often (in their own words) “the coax is a better radiator that the antenna”. It’s REALLY hard to tell if they’re fooling themselves and chasing unicorns, or if they’re actually onto something phenomenal, astounding, ground-breaking, industry-changing.

    Al MacDonald VE3TET (author of that ERC article), Paul Birke VE3PVB (co-author of the book), and several other PVA experimenters are all quite local to me, they often attend my club (Al in particular), and have presented there. I’ve also been to several of their presentations at other local clubs, and they often bring PVAs (including the UltraT in the picture) to our local hamfest to demo. I have tonnes of respect for all of them, they’ve put extraordinary work into this stuff, I wish I had more time to hack around with these antennas and help automate more scientific testing, help collect more DATA.

    In the meantime if anyone has any questions (or indeed ideas) for them, let me know (here on this thread is fine) and I’ll pass them on.

  5. I agree with Michael and NoseyNick. The physics behind antennas basically says, compactness/efficiency/bandwidth, pick (at most) any two.

    -Dipoles aren’t compact on HF, but they’re efficient and have relatively high bandwidth.
    -Dipoles can be made more compact, but doing so always involves increasing Q, which decreases bandwidth.
    -Magnetic loops can be compact and have reasonable bandwidth but they will have low efficiency.
    -Magnetic loops can be compact and efficient but will then have very low bandwidth.

    I would be very surprised if Poynting Vector antenna designs were able to somehow magically sidestep these constraints.

  6. Laughable!

    Why even discuss different “radiator” shapes, for instance? A capacity hat is a capacity hat! Waves the size of a bus can’t know the difference.

    Making crossed fields in one local region, does not, a propagating field, make.

    The capacity hats aren’t even enough, so they have to add tuning capacitors. Duh?

    So what is it, actually?

    A tuned, “electrically short” dipole. They’ve been known for centuries (well, using plural loosely here).

    It’s absolutely, fundamentally unpatentable on that merit. (It may be patentable simply because the overall mechanical design is different, or the tuning method (unlikely, given the lengthy history of tuning methods?), or simply because the patent system is absolutely retarded — ah, but that’s a rant for another day.)

    1. @T3sl4 – I think you may have misunderstood the concept Ted Hart (W5QJR) invented in the 1990’s. Ted is a HAM and worked for Harris Communications in the states (USA). You may need to look up what Harris does, quite impressive. Anyway, this Poynting Vector antenna Jenny List is writing about does not exploit what you are saying. It is quite revolutionary yet surprisingly simple to build. It is also known as the EH ANTENNA. It exploits “time domain” which allows the far field to be formed AT the antenna. This effectively reduces the size of the E and H fields to the physical sphere of the antenna. Since the E(electrical) and H(magnetic) fields have been reduced in magnitude, EMI has been virtually eliminated. When used for receiving, the EH Antenna allows transformation of radiated energy to the receiver terminals, but does not allow local E or H fields to be transformed, thus “noise” is eliminated. You can read Ted’s concept here: (EH ANTENNA FOR HAMS) and another (INTRODUCTION TO EH ANTENNAS) at same domain /book.pdf

      According to Ted many old timer HAMS think it just can’t work. However, the empirical proof is in the pudding as they say. Sometimes you have to think outside the box and be surprised what’s out there. He says the EH ANTENNA is not available commercially in USA or UK yet. I wonder why? I’ll bet our military (et al) is using them.

        1. Ostracus – Actually his website is in Georgia (USA) at I do not know why my link was in Russia. I also noticed that the an undo interest in this antenna in Russia. It should be an item OTS here in American and UK electronic stores like Radio Shack – et al. It’s quite popular in Japan and India (I think). All those tight apartment (aka FLATS) buildings and such.
          Here’s a quote from his home page:

          I have no idea who Edward Deming is. I’ve heard of Dr. W. Edwards Deming but I don’t get the connection.

  7. Much of this is not new. The CFA (crossed field antenna) dates back to the 1980s and this is an offshoot of it. Eventually I hope to publish a detailed review of DA BOOK (see Yahoo group of EH antennas).

    While there is a grain of truth in the EH antenna (and close relative super-T) their claims of low noise and high-Q improving reception are utter nonsense. As is the claim to eliminate common mode current with a link-coupling. IMO it’s just a radiating tuned circuit. Common mode radiation has been a persistent criticism. Put a £15 mobile whip on your car and compare to the EH antenna… EH will be worse.

    Remove the lower cylinder and it still radiates just as well… proving their “vector theory” is nonsense. The Poynting vector is not real anyway – it’s a mathematical concept used to measure power flow.

    My own take:

    And for the record AFAIK the military are not using them. In fact the UK MOD thinks they are crackpots.

    1. M0RZF – I defer to your expertise and background in the subject matter. However, your claim that the military thinks people like Ted Hart (W5QJR) et al are “crackpots” may be a little specious. The US military has been researching this since 1990’s when Ted was working on this. I have attached a once classified DTIC report (PDF) which is now declassified on this use of the Poynting Vector to make antennas smaller for things like missiles and such. It is really an “out of the box” thing and many old HAMS and RF engineers fail to understand how it really works.

      I personally think the darn thing is dangerous to humans to close to it. Ted made up a spreadsheet showing the voltages near the antenna – like one at 2-meters with only 5-watts input. It was 400Volts! But anyway it appears this thing is exploiting a time domain method of bringing the far field closer to the antenna.But I won’t pretend I understand it.

      I have found that Ted’s new ventures in Georgia (USA), involving a US military venture with DTI Corp (not related to DTIC) is drying up because another company bought them out and makes no mention of the EH Antenna model for it’s military operation. And his mention of a Japanese company who is commercializing the EH Antenna is also hitting a dead end. The Japanese website has been closed down with no forwarding website. I’m pretty sure Ted is no crackpot or a con-artist. However, something is strange about all of this.

      It appears the Russians have taken a keen interest in this EH Antenna and Ted has been hovering around them like many American celebrities have been doing lately. Any one who calls PUTIN “Putey” is a Russian groupy IMHO. His real nickname doesn’t even come close to that.

      That Yahoo group you mentioned doesn’t appear to allow anyone to view the messages even after joining. What’s up with that? And where can I view your “DA BOOK” – whatever that means?

      DTIC or Defense Technical Information Center – PDF file

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