[TowerTalk] repeating the N0AX/K7LXC studies

[Joe Subich, W4TV]

> If not having the 2nd antenna in the mainlobe, either to 
> receive the test signals or to transmit one, all results well 
> be misleading and it might happen that the worst antenna 
> gives the best result. That 2nd antenna postion must be 
> pretty heigh. Lets say the antenna to be tested is at 10m 
> height for the 20m test, then the other antenna 100m away 
> must be about 55m up!

This is a canard.  The groundwave signal is constant and 
all antennas will be effected equally so long as they are 
at a constant height above ground.  Since the ground is not 
perfectly conducting or perfectly reflecting, the direct 
field is not cancelled.  So long as the transmit and receive 
antennas have a line of sight path, any groundwave effect 
will be identical for all antennas of the same polarization. 

The N0AX/K7LXC protocol works because all tests are benchmarked 
against a dipole at the same height and orientation as the 
antenna under test.  By using a common reference and transmit 
to receive distances large enough to put the measurements in 
the square law region, differences in the range are eliminated 
and data collected on different ranges and at different times
may be compared directly.