[TowerTalk] Yagi gain question

[Bob Nielsen]

On Dec 23, 2005, at 7:22 AM, Stone, Gary R. wrote:

> Hi to all,
>
>
>
> First, I hope you all have a wonderful Holiday and Merry  
> Christmas.  Thanks
> for the help on this reflector this past year.
>
>
>
> I am now trying to sort out in my head a simple way to get a rough  
> idea
> about some gain calculations on a Yagi antenna.
>
> For example, if a Yagi has a gain of x db or x dbi (whichever) and is
> running a certain power then at what power level would you need with a
> vertical or dipole to roughly equal the Yagi?  Is there a simple  
> way to get
> a ROUGH idea and not a scientific solution?
>
>

Gary,

Compare the difference in gain between the yagi and a dipole. A  
dipole has a gain of 2.1 dBi, so compared to a yagi with a gain of  
8.1 dBi the difference would be 6 dB.  6 dB is a power ratio of 4, so  
you would need 4 times as much power to achieve the same signal  
level.  There are other considerations, of course, but you asked for  
the simple explanation.

73, Bob N7XY