Raise it, Karl !

a computer analysis by 1839


Hi Karl, here we are ;-)

This message sent by: Karldxiswl@aol.com

Hi folks
Little question concerning height of antenna.
I have heard arguments that an antenna should be at least 1/2 wave length off the ground in compared to its wave length to get full pattern on TX and TX side of things.

This is true. Here some pattern for a standard 3 element yagi. Different beams don't differ a lot.

The first one is the free-space pattern, just for reference.



On the second you can see the pattern for the same antenna over real ground at 4, 6, 8, 10, 12 meter high. Notice not only the increasing gain, but the dramatic increase in gain at low angles, the only ones of interest for dx.



On third you can verify gain at 10 degree. Here differences are very clear. I will raise your antenna to 20ft. when you ;-)



On fourth, just for fun ... a dipole at 11m is not so a bad performer, worst than a 3 element at 6m but better than the same yagi at 4m. The higher the better, at least since a full wave, 11m.



Now my beam is few feet below this 1/2 wave height of what i reckon should be min of 18ft for 11mb currently at 14 feet

If your antenna is 14ft over the roof that's enough. Roof is not ground. Otherwise ;-(

I hope I didn't overload your mailbox ;-)

Hi. 1 AT 1839 Paolo