Problem with nec2
To get started with nec2 I tried to simulate a simple dipole.
The graphical view of the pattern looks okay, however the gain seems
to be to high. To what are the DBs refered in the output file?
[...]
If I calculate the gain with the formula:
4 * Pi * r^2 * |E|^2
Gain = -----------------------
P_in * 2 * 120 * Pi
by using the E-Field magnitude values from nec2's output I get also
those very high values. (?)
PS, also confused by your formula. Which Value of E are you using? Are you
The formula should be correct:
I just use the magnitude value of the E Field. The intensitiy
W_rad is then 0.5 * |E|^2 / Z_w (E and H are in phase and
orthogonal in the far field)
The radiation density U is then r^2 * W_rad (Unit: Watt per solid angle)
The radiation density U_0 of an isotropic radiator with a total radiated
power P_rad is: P_rad / (4 * Pi).
The gain is then U/U_0 (or in dBi: 10*log(U/U_0) ).
trying to calculate the "Total radiated power" (TRP)? If so you need to
integrate the power density over a spherical region. The calculation is
Yes, but nec2 shows the total radiated power in its output.
As for your RP card, I notice that you are attempting to vary both "Theta"
and "Phi". I usually keep one fixed and vary the other, but to be honest I
am not sure if what you are doing is incorrect, although I notice that the
"Phi" pattern is only computed for one frequency. The only other difference
No thats no true. In the output file I can see E_phi as well as E_theta for
every combination of phi and theta (for every frequency).
I use the programm Xnecview to view the pattern and it has problems if you
don't have points over the full sphere.
is that I normally do not use gain averaging. Also using 1 degree
The average gain (over the full sphere) should probably be 1 (or 0 dBi).
I get 0.991.
Thanks for you help! The bad computation was caused by the stupid
segementation I had chosen.
Detlef
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