Near field vs Far field measurements at 2M
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
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