"Detlef Conradin" wrote in message
...
Hi

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?
Or what do I have to change to get the gain in dBi ?

Here is my input file:
-----------------------------------------
CM Test
CE
GW 1 20 0 0.005 0 0 7.5 0 0.01
GW 2 20 0 -0.005 0 0 -7.5 0 0.01
GW 3 1 0 -0.005 0 0 0.005 0 0.01
GE 0
EX 0 3 1 1 10. 0 0 0 0 0
FR 0 30 0 0 6. 1. 0 0 0 0
RP 0 37 72 1001 0. 0. 5. 5. 1000 1.
EN
-----------------------------------------

Detlef

PS:
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
trying to calculate the "Total radiated power" (TRP)? If so you need to
integrate the power density over a spherical region. The calculation is
greatly simplified if you take advantage of any natural symetry in the
radiation pattern -- i.e. integrate from axis end to axis end, then multiply
by 2*PI -- as in elementary calculus, you are using a single integral for a
"Solids of revolution" method, instead of a double (Surface integral).

If you are trying to caluculate the gain in a given direction you need to
take 20*log(E/Ei). Where E is the NEC calculated E field in the desired
direction, and Ei is the computed E field from an ideal isotropic source
with the same input power as the test antenna.

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
is that I normally do not use gain averaging. Also using 1 degree
increments does not seem to slow things down very much. With your RP card I
was also getting some weird pattern discontinuities.

Regards,

Frank