Historical use of the term dBi as antenna gain

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KX4O, Feb 2, 2017.

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  1. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    There is no such thing as a "ray" either....it's purely a mathematical construct. But it is IMMENSELY useful in describing most aspects of electromagnetic radiation, from DC to daylight.
    W6KCS likes this.
  2. AI3V

    AI3V Ham Member QRZ Page

    Another issue with the above mentioned colinear antenna gain plot.

    It is only accurate at a single frequency.

    Because of the way a phasing line works, with vertically stacked
    Vertical polarized antennas the beam will be shifted up or down from the horizon as the frequency is varied.

    Its a neat effect to simulate, and get a feel for the mechanical accuracy needed.

    Search for the antenna for the an/sps-48 radar for a great description of the effect.

  3. AA7EJ

    AA7EJ Ham Member QRZ Page

    OM ask a straight question and SOME regulars on this site rake him over the coals!
    He did not ask if he can build isotropic radiator etc etc etc
    You know-it-all geniuses just cannot read and just like to show-off what else besides topic YOU THINK you are experts in !

    I do not know when dBi was first used in publications , sorry John

    On the side note - using just antenna gain , in any units , is superfluous in 21th Century when we have means to mathematically describe other relevant antenna properties.
    Of course if majority of amateur radio hobbyist continue to measure antennas using cubits, the chance of them accepting 21th Century technology is slim to none.
    Off my soapbox.
    73 Shirley
    KX4O likes this.
  4. KX4O

    KX4O Ham Member QRZ Page

    Sure you can. I've done it for antennas at work and confirmed with measurements. Yes, design parameters have to be spot on, but it is demonstrably achievable.
  5. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    MY cubit happens to be PRECISELY half a meter....so it's very scientific. :)
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    God: "Don't worry, Noah, I'll tell you what a cubit is later."

    Noah: "No. What's an ark?"
    WB5YUZ likes this.
  7. KX4O

    KX4O Ham Member QRZ Page

    No one should make excuses for not desiring to learn. No one said antenna theory and practice was easy. Just don't blame the terminology used to profile it. We hams have a very poor record when it comes to spreading half-truths (gain of 2 dB?) and sometimes outright fiction (SlimJim has 3 dB gain over a J antenna). This happens in professional circles as well, but with much less frequency.
    KK5JY likes this.
  8. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Hence the phrase "Deus ex machina"*. ;)

    *"God from the machine"
  9. AA7EJ

    AA7EJ Ham Member QRZ Page

    Noah, how long can you tread water?

    .... you and me Lord ...
  10. AA7EJ

    AA7EJ Ham Member QRZ Page

    So YOUR cubit is meter / 2 - binary and digital !
    I 'll see you on 40 cubits band soon!

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