Justification for Full Antenna Analyser Over a NanoVNA

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by G0KDT, Jul 5, 2021.

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  1. SM0AOM

    SM0AOM Ham Member QRZ Page

    This is due to most Administrations not taking amateur radio seriously any more.
    They are nowadays run by accountants and lawyers who would prefer us to just go away, preferably quietly.

    73/
    Karl-Arne
    SM0AOM
     
  2. KJ7KNR

    KJ7KNR Ham Member QRZ Page

    Wow, to say that the wheels came off of this bus is an understatement!

    I'm just another dilettante, I guess, but I've been able to get QSO's with EFHW's with a 49:1 matching tx for distance exceeding 4000 miles using FT-8 (I like to use the with new antennas since the skimmers reporting can be handy info)

    OP, you know the limitations you're working within. You have a limited footprint with which to work, and you want to see what you can do using methods that have been long used within portable QRP community. While 80m can be a challenge it can be achieved by increasing the turns ratio while maintaining the impedance ratio (3:25 on a 240-43 or so, for instance). Since you clearly recognize that you're working with a compromised design from the beginning I'd say just work with what you have and see what you can achieve. There will always be people that will tell you that a given idea is no good or that modeling shows it's not tenable. While this may all be true, to some extent, it's results that count. Using varying homebrewed antennae, in Seattle, I've reached Antarctica, New Zealand, Australia, Japan, Sweden, and more. Some have been skimmer reports and some have been QSOs. This is in varying digital modes and CW. Again, results matter.

    If you've had enough of the VNA you can find used Rig Experts (I have an AA-54 I got on Craigslist) on Ebay for only a few hundred dollars if you want to stick with HF rather than all the way into UHF. I love it. I can interface it with my computer, get any info I need (for my purposes, anyway). Keep the VNA for later.

    Take it from me, a Jewish, Harley riding, mountain climbing, steel mill working, electrician and Old Antarctic Explorer (OAE). I can spread it around with the best of them but I still know when I step in it and when I don't.
     
  3. G0KDT

    G0KDT Ham Member QRZ Page

    As a closer to this tale of trying to get an EFHW to work I actually bought a commercial item having been made to feel that I was incompetent and knew nothing by one correspondent in this thread. Not only that I borrowed a RigExpert AA54 analyser to validate the Nano and to cross check everything.

    I also raised the antenna height at each end as best I could so about a 1/4wave up on 40m. The acid test was that the commercial antenna actually had a slightly worse tuning than the home brew item.

    So far none of the stuff that I have read across pages and pages of discussion (oft repeated with grandiose plots and analysis done and somewhat less than an explanation of what is being proffered) made one jot of difference with either homebrew or commercial antenna. Whatever it is at my location, maybe something about the ground terrain o_O, these Endfeds simply don't tune or work well here.
     
    W9WQA likes this.
  4. KM1H

    KM1H Ham Member QRZ Page

    And many are ignoring it as just another government intrusion in our increasing nanny state country.
     
    US7IGN likes this.
  5. W9WQA

    W9WQA Ham Member QRZ Page

    its ok in real life to be a cheapskate penny pinching tightwad as long as you save enuf in that process to buy
    every imaginable piece of test gear available for checking cheap wire antennas and others...
     
  6. US7IGN

    US7IGN Ham Member QRZ Page

    Hmm ... The fact of the matter is that when working portable, you have practically no restrictions. Neither the size of the antennas nor the noise.

    Maybe. Many are confused that an antenna that works great for ones does not work at all for others. Therefore, many are constantly trying different types of antennas. As me for example)
     
  7. G0KDT

    G0KDT Ham Member QRZ Page

    Well RSGB said they were working on the calculator solution here with ARRL.... I suggest if anybody is interested they take a look at the calculators prepared by Ofcom and RSGB so far. They are far from complete and will I suspect result in many doing exactly as you suggest that or just quit the hobby. Already there is a surge in newish HF kit turning up on the used market.
     
  8. SM0AOM

    SM0AOM Ham Member QRZ Page

    One may hope that both Ofcom and RSGB have sufficient knowledge of electromagnetics so they understand that it is impossible to make a simple "calculator" for estimating EMF exposure when near-field effects need to be included.

    A possible work-around could be to issue a blanket exemption for EMF evaluations for averaged power levels below, say, 50 W.

    To use higher power, a proper EMF exposure evaluation either made "by hand" or using 3D EM simulators would be required to be filed.

    Very few amateurs of today use power levels or antennas that pose any real EMF exposure problems, especially if they are located sufficiently far away so they cannot be touched.

    Remember, radio amateurs as a group are supposed to know how to understand and make at least simple EM calculations.

    This is one of the key aspects that differentiate us from other radio users who are restricted to type-approved equipment which is installed and maintained by professionals.

    73/
    Karl-Arne
    SM0AOM
     
    N0TZU likes this.
  9. G8FXC

    G8FXC XML Subscriber QRZ Page

    I sat and passed (with a good mark) the exam that you are on record as describing as one of the best - but there was no mention of EM calculations. For that matter, I passed a BSc in Electronic Engineering in the late seventies with a decent mark and don't recall ever being told how to calculate field strengths.

    Martin (G8FXC)
     
    WU9I and G0KDT like this.
  10. SM0AOM

    SM0AOM Ham Member QRZ Page

    After completing the course "Engineering Electromagnetics part B", we were expected to know how to calculate both near-field and far-field distributions around simple antennas such as dipoles and monopoles.

    Regarding the exams of yesteryear, they did not mention EM problems in much detail, but the study material for the "Class A" exam in 1972 contained stuff about how the near-fields varied along the length of an antenna element.

    Today, a lot more EM knowledge is required in the HAREC syllabus:

    upload_2021-7-28_9-5-45.png
    upload_2021-7-28_9-6-58.png

    upload_2021-7-28_9-2-26.png

    The German amateurs are required to have a quite deep understanding of EM concepts; below are a few typical questions about EM exposure concepts:

    upload_2021-7-28_9-40-26.png
    upload_2021-7-28_9-43-1.png
    upload_2021-7-28_9-45-16.png

    In my opinion, this is the level that should be required to use higher power levels than 50 W or so.

    73/
    Karl-Arne
    SM0AOM
     
    N0TZU likes this.

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