[TowerTalk] Takeoff angle

[Roger (K8RI) on TT]

As you "go up" in height (lower take off angle) those additional angles 
/ lobes become important and can fill in the intermediate distances.

73, Roger (K8RI)

On 7/24/2017 Monday 12:17 AM, Jim Brown wrote:
> I consider use of the words "takeoff angle" to be VERY misleading, and 
> cause a LOT of misconceptions. It is common to use the words "takeoff 
> angle" to define the vertical angle at which field strength is 
> greatest, and that the antenna only works at that angle. Nothing could 
> be further from the truth.
>
> Several years ago, I presented a modeling study showing that the low 
> angle radiation (15 degrees and below) of a horizontal antenna for 80 
> or 40 M continues to increase as the antenna is raised above ground.  
> I showed this by ignoring where the peak of the vertical pattern was, 
> instead looking only at the low angle field strength as the antenna 
> was raised. I didn't look at the SHAPE of the pattern -- instead, I 
> plotted curves of field strength at 5, 10, and 15 degrees as the 
> antenna was raised. A similar study for 20M produces comparable 
> results, taking wavelength into account. That study is presented in 
> the link below, starting around page 10.
>
> http://k9yc.com/AntennaPlanning.pdf
>
> That study is, of course, for "flatland," where terrain is not a 
> factor, but the same concepts apply in irregular terrain, except that 
> the terrain shifts the lobes up and down.
>
> 73, Jim K9YC
>
> On 7/23/2017 6:27 PM, Steve Maki wrote:
>> Err, we better keep straight whether we're speaking of heights above 
>> ground or takeoff angle. 
>
>
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-- 

73

Roger (K8RI)


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