[TowerTalk] Change in Frequency with Height above Ground

[Dan Maguire]

Don W7WLL wrote:
>>> Lowering the height of an antenna above ground, such as a beam, will cause the resonant freq to decrease, increase?

The "Resonate" button of the AutoEZ program makes short work of questions like this.  For example, create a 20m dipole model with an arbitrary length of 33.5 ft at height "H" above ground.  Set up a series of test cases with "H" ranging from 5 to 100 ft, all at 14.2 MHz.  Select all the "Freq (MHz)" cells and click the "Resonate" button.  Like so:

http://s33.postimg.org/u5kmyan7j/resonate1.png

Then tab to the Custom chart sheet and plot Frequency on the Y axis vs Variable H on the X axis.  Here are the results for three different EZNEC ground characteristics.

http://s33.postimg.org/69rm0qscf/resonate2.png

For more examples of using the "Resonate" button see Step 6 here:

http://ac6la.com/autoez.html

Or see the fifth and sixth bullets here:

http://ac6la.com/aecollection2.html

Dan, AC6LA