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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 absorbing material
(b) To compare my prototypes against a ref antenna (dipole) using a reflecting ground range.
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 plane wave.
SO I SUPPOSE THE MAIN QUESTION HERE IS HOW DO I GET THE ELEVATION INFORMATION ?