[TowerTalk] Yagi gain question

[K2EK@aol.com]

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

In theory this is true if both antennas are hung from clouds in free space.  
Over real ground, the yagi will perform significantly better than a similar 
situated dipole.

By way of example, I completed installation of my 90 foot tower late one 
weekend with the next few booked for family time.  Being impatient and darkness 
near, I hung a 15M driven element from the top...  Results suggested I was still 
in the dipole class rather than the robust signal I was expecting.  Needless 
to say, there was much concern considering the 4 tons of concrete plus another 
1/2 ton of tower, etc I had recently hauled up 70 feet of hillside.  Later on 
after adding a boom and 2 more elements were like turning on a switch.  
Believe me, it was a lot better than 6 DB!!

73 de Bill
K2EK