"Steve Reinhardt" wrote in message
...
Gentlemen,

If a man was of a mind to try to get some approximate antenna gain
comparisons, how many wavelengths distant might you like to separate the
antennas?

The proposed scenario is this: make a pair of 2M dipoles, one for
reference, one for receive. I was planning on using the local high school
football field, which is on the order of 50 wl, give or take. Transmit a
few mW at the design frequency, measure the signal strength, then repeat
with an alternate antenna, say a j-pole, collinear, or something else.

Now, this leaves out a whole bunch of useful information, that would be
tough for me to measure, like spherical gain distribution, etc. I'm hoping
for a figure of merit for the actual implementation of the tested antenna.
(Which, as you can imagine, I could model and save myself the
aggravation.)

I was pondering all this, when it occurred to me that I could not easily
determine when I get to the point where the square law behavior dominates.
I've seen a couple of equations relating the antenna dimension to
wavelength, but I must be really stupid today, because it's just not
sinking in.

Anyone care to comment?

73,
Steve
W1KF

Hi Steve

It is fairly easy to record exact radiation patterns of "2 meter" antennas
at 137 MHz, using NOAA satellites at the Illuminator. If you have any
interest in the details, you can contact me anytime.
Patrik Tast developed a (free) program for me that produces elevation
plane patterns of the antenna as the NOAA satellite passes over. Since each
satellite passes over 6 or 8 times per day, decent hemispheric patterns can
be made.
I'd guess that the plot of the antenna pattern, when using Patrik's
program is more accurate than any other method when evaluating ground based
"2 meter" antennas. I am open to learning where I'm wrong about the
accuracy.

Jerry