Rohit wrote:
Hi all,
With the same setup as i have stated before, I have observed the
pattern by changing the spacing between the 2 antennas. For every 1
wavelength increase in spacing i am abserving one lobe around 90deg.
As the spacing becomes lage multiple of wavelength, the ripples
magnitude increase to greater extent. Can someone explain this. With
the experiment i've done, it indicates that for the spacing of 1
wavelength i get the best pattern without ripples.



It is the constructive and destructive mixing of the rf being emitted by
your antenna's. Your results are exactly correct. It is the reason that
twin cb radio antenna's don't really work on an 8 foot wide truck. At
that spacing they are only a fraction of a wave length apart and act as
one antenna.

Dave WD9BDZ

( I am working in GHz range and so the spacing of multiples of
wavelength means it will be only few cms.)
One more observation i have made is that i have placed my antennas on
a rectangular plate and then on a curved surface. The former setup
gives me around -20db gain at 270deg, i.e back side of the rectangular
plate whereas in the latter case there is no such diffraction effect.
Why is it so?

Also i want to know how is the minimum spacing between antennas
decided ?

On 15 Feb 2007 03:37:43 -0800, Rohit wrote:
Also i want to know how is the minimum spacing between antennas
decided ?

It's *never* "decided". It is constantly _argued._ Just hang around here.