On Sep 4, 3:37Â*am, Szczepan BiaÅ‚ek wrote:
U¿ytkownik napisa³ w ...
On Sep 3, 10:29 pm, Jeff Liebermann wrote:



On Thu, 3 Sep 2009 19:11:42 -0700 (PDT), wrote:
How in the heck are you going to
get **ANY** vertical radiator to have a truly isotropic pattern?
It's impossible. An isotropic pattern is a theoretical pattern
in which radiation is equal in all directions. Such a pattern
does not exist with real antennas.

A real isotropic radiator may not exist, but one can get fairly close.
If you believe the model, the total error is 0.44 db. See:
http://802.11junk.com/jeffl/antennas/isotropic/index.html
The NEC2 deck is under the photo labeled "main".

I once built one of these antennas on roughly 444MHz out of cardboard
and magnet wire. The oscillator was a small crystal can oscillator
running from a 9V battery to avoid having the feed coax wrecking the
pattern. The impedance was nowhere near 50 ohms and required a bit of
matching to get the VSWR down. I'm now digging for the photos.

I used a piece of string to maintain a constant radius, a tiny pickup
loop at the end of a length of coax cable running inline with the
string, and eventually going to my antique HP spectrum analyzer. On
the 2dB/div scale, it was a fairly good approximation of an isotropic
radiator with errors mostly caused by indoor reflections and
interference with the bench.

Sure, you can get fairly close to isotropic with the right

system, but how are you going to do it by tipping a
vertical? Â*The likely results do not fit my idea of isotropic.

"An isotropic radiator is a theoretical point source of waves which exhibits
the same magnitude or properties when measured in all directions".
The only way to make the real point source is the proper tipping. Of course
it must be a monopole.
S*

Excellent. I am so happy that somebody out there is not following the
pied pipers of denial.
Thanks for your input.