#!user/bin/perl;
#dipole.pl

# ###########################
# Simple programme to calculate approximate dipole lengths, used in talk 
# at RSGB HF & IOTA Convention, 24-Oct-04
#
# Version: 1.0 (20 Oct 04)
#
# Copyright (c) 2004 Dominic Smith, M0BLF
# Released under GNU GPL available from 
# http://www.gnu.org/copyleft/gpl.html
#
# ----- LICENCE -----
# 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 2
# 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, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
# --------------------
# 
# For information about this programme, email m0blf@domsmith.co.uk
# ###########################

use strict;
use warnings;

our $freq;
our $wave;
our $halfwave;
our $halfwave_imp;
our $quarterwave;
our $quarterwave_imp;

sub round 
	{
	my $roundthis;
	# Rounds to three decimal places
	my($roundthis) = shift;
	$roundthis = $roundthis*1000;
	$roundthis = int($roundthis);
	$roundthis = $roundthis/1000;
	return ($roundthis);
	}

system("cls"); 			#Warning - will only work on DOS-based platforms!	
print "Dipole Calculator\n";
print "------ ----------\n";
print "Dipole Calculator v 1.0, by Dominic Smith M0BLF \nSee source code for GPL licence information\n";
print "-----------------\n\n";
print "Please input a frequency in Megahertz, between 0.1 and 1325:\n";
chomp($freq = <STDIN>);
if ($freq > 0.1 && $freq <1325)
	{
	$wave = round(300/$freq);
	$halfwave = round($wave/2);
	$halfwave_imp = round($halfwave/0.3048);
	$quarterwave = round($wave/4);
	$quarterwave_imp = round($quarterwave/0.3048);
	print "\n\n";
	print "\tFrequency\t=\t$freq MHz\n";
	print "\tWavelength\t=\t$wave m\n";
	print "\n";
	print "\tTotal Length\t=\t$halfwave m ($halfwave_imp ft)\n";
	print "\n";
	print "     $quarterwave m                  $quarterwave m\n";
	print " --------------------\\  \/-------------------\n";
	print "                      ||\n";
	print "     $quarterwave_imp ft                  $quarterwave_imp ft\n";
	print "\nAll measurements are rounded and are approximate.  \nDon\'t forget to make the dipole too long first - \n";
	print "It\'s easier to cut wire than add more afterwards!\n";
	}
else
	{
	print "Aborting.  Frequency out of range.\n";
	}
# EOF