// JavaScript Document
function calculate3ElementYagi(form)
// calculate the dimensions for various parts of a 3-element yagi
	{
		var reflector_factor = 501;
		var driven_factor = 473;
		var director_factor = 445;
		var frequency_factor = 468;
		var element_diameter = 0.375;
		var frequency = form.frequency.value;
	
		if (frequency > 0)
			{
				var reflector = reflector_factor / frequency;
				var half_reflector = reflector / 2;
				var driven_element = driven_factor / frequency;
				var half_driven_element = driven_element / 2;
				var director = director_factor / frequency;
				var half_director = director / 2;
				var spacing = (((frequency_factor / frequency)*2)*.2);
				var boom = ((spacing * 2) + element_diameter);
				var half_boom = boom / 2;
				var turning_radius = Math.pow((Math.pow(boom/2.0,2.0) + Math.pow(reflector/2.0,2.0)),0.5);
			
				form.driven_element_decimal.value = roundNumber(driven_element,2)+" ft";
				form.driven_element_fractional.value = fractional_feet_inches(driven_element);
				form.driven_element_meters.value = meters_from_feet(driven_element)+" meters";
				form.half_driven_element_decimal.value = roundNumber(half_driven_element,2)+" ft";
				form.half_driven_element_fractional.value = fractional_feet_inches(half_driven_element);
				form.half_driven_element_meters.value = meters_from_feet(half_driven_element)+" meters";
				form.director_decimal.value = roundNumber(director,2)+" ft";
				form.director_fractional.value = fractional_feet_inches(director);
				form.director_meters.value = meters_from_feet(director)+" meters";
				form.half_director_decimal.value = roundNumber(half_director,2)+" ft";
				form.half_director_fractional.value = fractional_feet_inches(half_director);
				form.half_director_meters.value = meters_from_feet(half_director)+" meters";
				form.reflector_decimal.value = roundNumber(reflector,2)+" ft";
				form.reflector_fractional.value = fractional_feet_inches(reflector);
				form.reflector_meters.value = meters_from_feet(reflector)+" meters";
				form.half_reflector_decimal.value = roundNumber(half_reflector,2)+" ft";
				form.half_reflector_fractional.value = fractional_feet_inches(half_reflector);
				form.half_reflector_meters.value = meters_from_feet(half_reflector)+" meters";
				form.boom_decimal.value = roundNumber(boom,2)+" ft";
				form.boom_fractional.value = fractional_feet_inches(boom);
				form.boom_meters.value = meters_from_feet(boom)+" meters";
				form.half_boom_decimal.value = roundNumber(half_boom,2)+" ft";
				form.half_boom_fractional.value = fractional_feet_inches(half_boom);
				form.half_boom_meters.value = meters_from_feet(half_boom)+" meters";
				form.spacing_decimal.value = roundNumber(spacing,2)+" ft";
				form.spacing_fractional.value = fractional_feet_inches(spacing);
				form.spacing_meters.value = meters_from_feet(spacing)+" meters";
				form.turning_radius_decimal.value = roundNumber(turning_radius,2)+" ft";
				form.turning_radius_fractional.value = fractional_feet_inches(turning_radius);
				form.turning_radius_meters.value = meters_from_feet(turning_radius)+" meters";
			}
		else
			{
				clearResults(form);
			}
	}

function clearResults(form)
	{
		form.driven_element_decimal.value = "";
		form.driven_element_fractional.value = "";
		form.driven_element_meters.value = "";
		form.half_driven_element_decimal.value = "";
		form.half_driven_element_fractional.value = "";
		form.half_driven_element_meters.value = "";
		form.director_decimal.value = "";
		form.director_fractional.value = "";
		form.director_meters.value = "";
		form.half_director_decimal.value = "";
		form.half_director_fractional.value = "";
		form.half_director_meters.value = "";
		form.reflector_decimal.value = "";
		form.reflector_fractional.value = "";
		form.reflector_meters.value = "";
		form.half_reflector_decimal.value = "";
		form.half_reflector_fractional.value = "";
		form.half_reflector_meters.value = "";
		form.boom_decimal.value = "";
		form.boom_fractional.value = "";
		form.boom_meters.value = "";
		form.half_boom_decimal.value = "";
		form.half_boom_fractional.value = "";
		form.half_boom_meters.value = "";
		form.spacing_decimal.value = "";
		form.spacing_fractional.value = "";
		form.spacing_meters.value = "";
		form.turning_radius_decimal.value = "";
		form.turning_radius_fractional.value = "";
		form.turning_radius_meters.value = "";
	}
	
function checkEnter(form)
	{
		var characterCode
		if (window.event)
			{ 
				e = window.event;
				if (e.keyCode == 13)
					{
						calculate3ElementYagi(form);
					}
			}
	}