[Towertalk] Testing Equipment? (Important Addendum)

[Chuck Counselman]

At 3:52 PM -0800 12/12/02, Dino Darling k6rix wrote:
>When a manufacturer tests antennas on a range, what equipment is 
>used?  A field strength meter?  A spectrum analyzer?

In my first response I neglected to mention something very important: 
calibration.

To calibrate measurements of antenna gain, a "standard gain" antenna 
is used.  This is an antenna whose gain is accurately known -- 
somehow.  Simple examples of standard gain antennas are the microwave 
horn and the cylindrical (uniform diameter wire/rod/tube) dipole. 
Their gains can be calculated accurately from E-M theory.

The gain of an unknown antenna is determined by comparison with a 
standard antenna.

By far the hardest part of antenna gain measurement is dealing with 
reflections or scattering from nearby objects/surfaces.  The use of a 
standard-gain antenna does not solve this problem because the pattern 
of the standard-gain antenna is never the same as that of the antenna 
under test.

73 de Chuck, W1HIS