Page 2 of 2 FirstFirst 12
Results 16 to 18 of 18
  1. #16

    Re: Vhf aerial question

    Quote Originally Posted by Owen View Post
    Penny has just dropped as to the reason why only half the length is typical.
    1.8m if a full wave at VHF frequency. Therefore it has a null at the horizon if mounted vertically. The signal is like this 8
    It will perform great if laid flat and used as a directional antenna in yagi or quad config but useless in a boat.
    Therefore a 1/2 wave is used with the ground plane forming the other half.
    Which fits exactly with the observations above re build.

    So if we assume they are all half wave and if the two lengths have the same gain, measured in the same way, then height is key.


    My apologies for confusing the issue.
    LOL. No need to apologize. You sound a bit like me Owen - I've forgotten more about what I learned at tafe than I remember. The days of remembering all the formulae for wavelength calculation, etc are loooooong gone.

    I suspect the higher gain full length antennas are using a 3/4 wavelength set up but I never had one come back stuffed so I could investigate
    "I soak the worms in rum. The fish love em and the worms die happy"
    "Alcohol is not the solution to your problems...................but then again, neither is milk"

  2. #17

    Re: Vhf aerial question

    There are VHF antenna then there are VHF antenna, height is the all mighty superior requirement by far .... but just be aware of the different means by which different manufacturers utilize ground plane requirements.

  3. #18

    Re: Vhf aerial question

    http://www.jpole-antenna.com/2012/02...ommunications/

    This one helped me mate, just need to hit up the old metric converter. I hope this helps!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Join us