diff --git a/bendrtd_eval.m b/bendrtd_eval.m
new file mode 100644
index 0000000..6e71de1
--- /dev/null
+++ b/bendrtd_eval.m
@@ -0,0 +1,38 @@
+## Copyright (C) 2018 Jens
+##
+## This program is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program. If not, see .
+
+## -*- texinfo -*-
+## @deftypefn {} {@var{retval} =} bendrtd_eval (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens
+## Created: 2018-09-05
+
+function [retval] = bendrtd_eval (radius_mm)
+
+%radius_mm = 0.1;
+bend_angle_deg = 90;
+probe_diameter_mm = 25.4/4;
+probe_length_y_mm = 280;
+probe_length_x_mm = 50;
+
+h = radius_mm*sin(2*pi*bend_angle_deg/360)
+U = 2*pi*radius_mm*bend_angle_deg/360;
+probe_length = probe_length_y_mm + probe_length_x_mm + 2*U
+
+
+endfunction
diff --git a/common/print_parameters.m b/common/print_parameters.m
new file mode 100644
index 0000000..fdd7c8f
--- /dev/null
+++ b/common/print_parameters.m
@@ -0,0 +1,16 @@
+function print_parameters(params, units)
+align = 32;
+names = fieldnames(params);
+for n=1:length(names),
+ fprintf('%s', names{n});
+ remain = align - length(names{n});
+ if remain < 0
+ error('Invalid variable length!');
+ else
+ for j=1:remain
+ fprintf(' ');
+ end
+ fprintf('= %g %s\n', params.(names{n}), units.(names{n}));
+ end
+end
+endfunction
diff --git a/garage_results.m b/garage_results.m
new file mode 100644
index 0000000..9660ded
--- /dev/null
+++ b/garage_results.m
@@ -0,0 +1,32 @@
+## Copyright (C) 2018 Jens
+##
+## This program is free software: you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program. If not, see
+## .
+
+## -*- texinfo -*-
+## @deftypefn {} {@var{retval} =} garage_results (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens
+## Created: 2018-12-10
+
+function garage_results()
+
+y = load("/home/jens/garage_y.dat", '-ascii');
+bits = load("/home/jens/garage_bits.dat", '-ascii');
+plot(y(:,1), y(:,2), bits(:,1), bits(:,2), 'xr'); grid;
+
+endfunction
diff --git a/tuneable_bandpass.m b/tuneable_bandpass.m
new file mode 100644
index 0000000..c5f288c
--- /dev/null
+++ b/tuneable_bandpass.m
@@ -0,0 +1,98 @@
+## Copyright (C) 2018 Jens Ahrensfeld
+##
+## This program is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program. If not, see .
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{retval} =} tunable_bandpass (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens Ahrensfeld
+## Created: 2018-11-26
+## taken from: https://www.mwrf.com/components/bandpass-filters-feature-wide-tuning-ranges
+
+function tuneable_bandpass(varargin)
+
+params = struct ('f_low_Hz', 40e6, 'f_high_Hz', 800e6, 'f_step_Hz', 1e6, 'B_geo_Hz', 10e6, 'R_geo', 500, 'R_0', 50, 'k_gamma', 1.0);
+units = struct ('f_low_Hz', 'Hz', 'f_high_Hz', 'Hz', 'f_step_Hz', 'Hz', 'B_geo_Hz', 'Hz', 'R_geo', 'O', 'R_0', 'O', 'k_gamma', '');
+
+% Parse parameters
+names = fieldnames(params);
+for k=1:nargin-1,
+ for n=1:length(names),
+ if strcmpi(varargin{k}, names{n})
+ params.(names{n}) = varargin{k+1};
+ end
+ end
+end
+
+print_parameters(params, units)
+
+f_low_Hz = params.f_low_Hz; % Minimum tunable filter center frequency (Hz)
+f_high_Hz = params.f_high_Hz; % Maximum tunable filter center frequency (Hz)
+
+B_geo_Hz = params.B_geo_Hz; % -3 dB RF filter bandwidth (in Hz) at the geometric center frequency
+R_geo = params.R_geo; % Internal filter impedance (in O) at the geometric center frequency of the filter
+R_0 = params.R_0; % Port impedance, usually taken as 50 O
+
+k_gamma = params.k_gamma; % Constant value. A value of ? = 1.0 results in a constant-Q filter design,
+ % while a value of ? = 2.0 results in a constant-bandwidth filter design.
+ % A value between one and two will yield a blend of the two filter characteristics.
+ % Inductor Q values will be more critical as the value of ? is increased.
+
+f_step_Hz = params.f_step_Hz;
+f_Hz = f_low_Hz:f_step_Hz:f_high_Hz;
+omega = 2*pi*f_Hz;
+
+f_geo_Hz = sqrt(f_low_Hz*f_high_Hz) % Hz
+omega_geo = 2*pi*f_geo_Hz % rad/sec
+
+% Design I.
+R_t = R_geo*(omega/omega_geo).^k_gamma; % Equ. (1)
+L_c = R_geo/omega_geo % Equ. (2)
+
+C_tgeo = 1./(pi*sqrt(2)*R_geo*B_geo_Hz) % Equ. (3)
+L_eff = 1./(omega_geo^2*C_tgeo) % Equ. (4)
+L_r = L_eff * L_c / (L_c - L_eff) % Equ. (5)
+
+C_t = (omega_geo./omega).^2 * C_tgeo; % Equ. (6)
+
+% Tuning capacitances C1 and C2 are given by Eqs. 7 and 8
+C_1 = (omega*R_0).^(-1) .* sqrt((omega_geo./omega).^k_gamma * (R_0/R_geo) + omega.^2.*C_t.^2*R_0*R_geo.*(omega/omega_geo).^k_gamma - 1); % Equ. (7)
+C_2 = ((omega.^2.*C_t)./((omega_geo./omega).^(2*k_gamma) .* (1/R_geo)^2 + (omega.*C_t).^2) - (omega.^2*R_0^2.*C_1)./(1+(omega*R_0.*C_1).^2)).^(-1); % Equ. (8)
+
+C_1_geo = (omega_geo*R_0).^(-1) .* sqrt((omega_geo./omega_geo).^k_gamma * (R_0/R_geo) + omega_geo.^2.*C_tgeo.^2*R_0*R_geo.*(omega_geo/omega_geo).^k_gamma - 1) % Equ. (7)
+C_2_geo = ((omega_geo.^2.*C_tgeo)./((omega_geo./omega_geo).^(2*k_gamma) .* (1/R_geo)^2 + (omega_geo.*C_tgeo).^2) - (omega_geo.^2*R_0^2.*C_1_geo)./(1+(omega_geo*R_0.*C_1_geo).^2)).^(-1) % Equ. (8)
+
+subplot (2,1,1)
+plot(f_Hz*1e-6, C_1*1e12); grid; xlabel("f/MHz"), ylabel("C_1 [pF]");
+subplot (2,1,2)
+plot(f_Hz*1e-6, C_2*1e12); grid; xlabel("f/MHz"), ylabel("C_2 [pF]");
+
+% Design II.
+L_c = R_geo/omega_geo; % Equ. (9)
+L_eff = R_geo./(pi*sqrt(2)*B_geo_Hz); % Equ. (10)
+L_r = L_eff - L_c; % Equ. (11)
+C_tgeo = 1./(L_eff*omega_geo^2); % Equ. (12)
+C_t = (omega_geo./omega).^2 * C_tgeo; % Equ. (13)
+a = -omega.^2*R_0.*R_t; % Equ. (14)
+b = 1./C_t; % ...
+d = R_t/R_0; % Equ. (14)
+alpha = (d-b.^2/a)./(1+b.^2/a - d); % Equ. (15)
+beta = (b./a)./(1 + b.^2/a - d); % Equ. (16)
+C_2 = alpha.*C_1 + beta; % Equ. (17)
+
+endfunction
+