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. *

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
#http://802.11junk.com* * * * * * *
#http://www.LearnByDestroying.com* * * * * * * AE6KS

You cannot assume that one who makes an accusation has the status of
education to match his veracity. The person who stated that it is an
impossibility does not even posses a high school diploma. Climbing on
the back of his statements puts you back on the stage again!