Isotropic Antennas - dBi vs dBd - and Negative Gain

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  • Опубліковано 12 вер 2024

КОМЕНТАРІ • 61

  • @rrrandommman
    @rrrandommman 5 місяців тому +3

    You so often make videos on radio theory topics I've been meaning to get my head around, you're a credit to the community, 73.

  • @snokones
    @snokones 5 місяців тому +2

    But this is why i keep two antennas. I have my 12.4m Signature, That i absolutely love. And a 135' Doublet fed with 600ohm. If one doesn't get the contact, the other will.

  • @robertabbott7770
    @robertabbott7770 5 місяців тому +2

    kept staring at the dot - We love Lord Callum - We love Lord Callum - We love Lord Callum !!!🤣🤣

    • @rrrandommman
      @rrrandommman 5 місяців тому +1

      We love Lord Callum. @_@

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      HAHA.. Crazy! You've been watching too many of my videos!!

  • @grahammoucka7270
    @grahammoucka7270 5 місяців тому

    "poke a balloon in the middle" 🤯 such a simple explanation to understand 😂 thanks!

  • @sunn1011
    @sunn1011 5 місяців тому

    I love when you draw things! Have you ever thought of raffling off those sketch books for charity?
    They are works of art technically.😊 Thanks again for all that you do!

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      Good point.. I keep meaning to do something with them...!

  • @BrokenSignal
    @BrokenSignal 5 місяців тому

    Love this, very good videos explaining dB!

  • @j.p.thearmoredchef
    @j.p.thearmoredchef 5 місяців тому

    Fantastic explanation!

  • @Rubedo777
    @Rubedo777 5 місяців тому +1

    R..iii..ght errr I’ll take your word for this Cal 😵‍💫 I’m really p.poor at anything maths… I’ve just got plus minus times divide understood, coz I’m thick I suppose… 🧐 still passed my G0 licence though way back when I was just an harmonic 😆 🤣 💙

  • @migalito1955
    @migalito1955 5 місяців тому

    I've always wanted to build a 2 element 40 meter Yaggi. I have the space for it, but often I am just too busy elsewhere. I used to build up to 4 element vertical 10 meter Yaggis like a rope ladder and I used a 12.5 calculated impedance at the feedpoint to make them very short in boom length. I then used a folded dipole as the driven element to alter impedance back to about 50 ohms. They worked really well, unfortunately the technique does not scale up to 40 meter size easily.
    You guys, have likely already had the fun of building one but I need a piece of the fun pie too & antennas certainly are fun to make effective....

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому +1

      Well.. It would scale - you just need a huge tower - and some extra money! PS - Great technique for the impedance transformation!

    • @paulsengupta971
      @paulsengupta971 5 місяців тому +1

      What about building a 40m Moxon?

    • @migalito1955
      @migalito1955 5 місяців тому

      @@paulsengupta971 You know, that actually is a good idea... i like it.

    • @migalito1955
      @migalito1955 5 місяців тому

      @@DXCommanderHQ Spot on with my wallet is to thin for the towers needed.

    • @paulsengupta971
      @paulsengupta971 5 місяців тому

      @@migalito1955Alternatively, do what Callum has done, create a vertical two element beam using quarter wave ground plane verticals, either phased or passive.

  • @maciejkowalczyk23
    @maciejkowalczyk23 5 місяців тому

    thanks Call 73!

  • @DonzLockz
    @DonzLockz 5 місяців тому +1

    So, more banana's are better?🍌😂
    Thanks Callum. ;)

  • @k9eihamradio
    @k9eihamradio 5 місяців тому

    Cal. Thanks for showing the dBb ruler, or dB relative to bananas measurerer. :) Ha!

  • @m0aze611
    @m0aze611 5 місяців тому

    Hi Callum, trying to access your website via iPad or iPhone and I get a notification that it couldn’t establish a secure connection to the server. Maybe an Apple Safari thing dont know. Regards Mike

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      Hmmm. We're through CloudFlare.. It might be a glitch.

  • @rickbattle5706
    @rickbattle5706 5 місяців тому

    Is it legal in the UK to stick your fingers in a balloon? Goodness, I must be missing out. Great Video as usual. KB3NG

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      Yes, new legislation was passed last year!

  • @rayb228
    @rayb228 5 місяців тому

    Helpful, now i'll have to watch the Db vid AGAIN. Maths defeats me especially when - x - = + and then there's 3.142........where does it end.........Wigglies and Bananas. Good Grief !

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      Ah.. 3.142. At least you know off by heart!

    • @paulsengupta971
      @paulsengupta971 5 місяців тому

      I just thought a downside of using dBb (relative to a banana). Are we talking about distance/length or are we talking about calories? How many dBb does a pie have relative to a banana?

    • @rayb228
      @rayb228 5 місяців тому

      if UK try SLIMMING WORLD RADIO , Sir ;-)@@paulsengupta971

  • @stargazer7644
    @stargazer7644 5 місяців тому

    The Sun is a pretty good isotropic radiator.

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      Oh yes! It's just a million times bigger than this planet..!

  • @paulsengupta971
    @paulsengupta971 5 місяців тому

    Everything's relative. Especially in Alabama. New measurement, dBb. Relative length to a banana. As for poking fingers in balloons and bulges changing shape, my belt does that to my stomach.

  • @Siskiyous6
    @Siskiyous6 5 місяців тому

    I dislike dBi because it changes with height and the quality of the ground, using it for comparison takes the thoroughness of a man like Cebik, I would say no one else ever explains their comparison in enough detail for it to be even worth reading.

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому

      Well dBi NEVER changes, that's the point.. Everything else does though! :)

    • @paulsengupta971
      @paulsengupta971 5 місяців тому

      Antenna fiends change. Entropy. Something to do with putting up antennas while drinking cups of tea.

    • @Siskiyous6
      @Siskiyous6 5 місяців тому

      @@DXCommanderHQ my bad, I am a terrible editor, I meant dbd

  • @jeffmerlin2580
    @jeffmerlin2580 5 місяців тому

    1:09 Fill the balloon with water, then the analogy works. 🙂 Water in incompressible, air is not. Anyway, that nitpicking. Nice video, good explanation.

    • @DXCommanderHQ
      @DXCommanderHQ  5 місяців тому +2

      Yes OK.. I would like you to see your hand compress air :)

    • @jeffmerlin2580
      @jeffmerlin2580 5 місяців тому

      @@DXCommanderHQ If you're as old as me, you've probably done that with a bicycle pump. 🙂

  • @ke8wlw
    @ke8wlw 5 місяців тому

    First. Good afternoon cal

  • @terencebarfield5864
    @terencebarfield5864 18 днів тому

    Sir your video being good - down side to this: you never do sketches to help Beginners to understand to what you are trying say and do or teach

  • @jest.s50si83
    @jest.s50si83 5 місяців тому

    Heii Call🫡 I'm steal here and watchig you👻 My friend

  • @JayN4GO
    @JayN4GO 5 місяців тому +1

    Dbi needs to be canned. Dbd and dbd over average ground more reasonable. These companies will never understand that true gain sells. Innov meh they’re getting better. Not quite there yet.

    • @petemillis4666
      @petemillis4666 5 місяців тому +1

      dBi does not "need to be canned". Reference to a theoretical isotropic radiator is a perfectly scientific and valid comparison. What needs to happen is that amateur radio ops / hams need to partake in self learning and critical thinking, and gain a decent understanding of the comparison to various reference antennas.

    • @JayN4GO
      @JayN4GO 5 місяців тому

      @@petemillis4666 there shouldn’t be 3 imaginary made up reference points to base scientific theories. Make the shit realistic

    • @dondonaldson1684
      @dondonaldson1684 5 місяців тому

      ​@@JayN4GO"dBd over average ground" isn't realistic. I understand your point but as soon as "average" is brought in to the discussion it infers statistical mean, standard deviation and variance...

  • @williamkizer3445
    @williamkizer3445 5 місяців тому

    Real explanation very cool 😎KQ4OHB

  • @dondonaldson1684
    @dondonaldson1684 5 місяців тому

    Then there is dBDXC 😂