function s = gr12(par,c)
% s = gr12(par,c)
% 12-Element-Group Antenna for 144 MHz
% par :  Vector of 5 length parameters:
%        [length of dipoles ,...
%         length of reflectors ,...
%         distance between dipoles and reflectors ,...
%         horizontal spacing between elements ,...
%         vertical distance between dipoles ]
% c :  complex amplitude of excitation

% Author:  Klaus von der Heide, e-mail:  dj5hg@qsl.net

% Defaults
% ========
if nargin<2  c = 1; end
if nargin<1
   ld = 1.080;           % length of dipoles
   lr = 1.030;           % length of reflectors
   dr = 0.400;           % distance between dipoles and reflectors
   dh = 0.150;           % horizontal spacing between elements
   dv = 1.100;           % vertical distance between dipoles
else
   ld = par(1);          % length of dipoles
   lr = par(2);          % length of reflectors
   dr = par(3);          % distance between dipoles and reflectors
   dh = par(4);          % horizontal spacing between elements
   dv = par(5);          % vertical distance between dipoles
end   

% Constants
% =========
m  = 7;                  % number of segments per element

% Construction
% ============
for k=1:3
   dip{k} =  wire([ 0  -ld      (k-2)*dv],[ 0  +ld      (k-2)*dv], 0.002, 7);
   ref{k} = wires([-dr -lr-dh/2 (k-2)*dv;  -dr +lr+dh/2 (k-2)*dv],...
                  [-dr -dh/2    (k-2)*dv;  -dr +dh/2    (k-2)*dv], 0.002, 7);
end
trm{1} = transmission([0 0 0],[0 0 -dv],dv,-1000); 
trm{2} = transmission([0 0 0],[0 0 +dv],dv,-1000);
exc    = excitation([0 0 0],1);
s = comment(construct(dip{:},ref{:},trm{:},exc),{'12-Element-Gruppe';'144 MHz'});
