How to measure antenna gain etc - RF Cafe Forums
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Post subject: How to measure antenna gain etc
Posted: Mon Jun 20, 2005 6:45 am
I need to determine the gain and hopefully the radiation
pattern of a number of small prototype antennas.
All the antennas are for operation at around 400
MHz and are half the size or less than a dipole
at this fequency. So..........how can I do this
After some research I find that the recommended
method is either:-
(a) to compare my prototypes
against a ref antenna (dipole) in a room lined with
(b) To compare my prototypes
against a ref antenna (dipole) using a reflecting
I dont have access to the absorber
room so it seems that I need to go with option (b).
Heres where it gets interesting..........
The literature I have read suggests that in
the reflecting ground range method you must set
the antenna heights to the lowest height signal
maxima. Now unless I am missing the point this only
gives the PEAK gain that you could possibly get
with the particular antenna ? I assume that going
further I can rotate the antenna under test to determine
the azimuth pattern but I can not see how I can
get any elevation pattern information ? The only
thought on this was maybe to change the orientation
of the reference antenna and the antenna under test
(dipole goes from vertical to horizontal etc) this
MIGHT allow the elevation to be taken from the azimuth
measurements whilst still picking the peak signal
In additon to the above the literature
I have found on the subject points out that there
is a minumum recommended range between the two antennas
on the range. This is called for (I think) to ensure
the wave front at the antenna under test is a uniform
SO I SUPPOSE THE MAIN QUESTION
HERE IS HOW DO I GET THE ELEVATION INFORMATION ?
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