{"id":99,"date":"2015-09-03T15:10:00","date_gmt":"2015-09-03T15:10:00","guid":{"rendered":"http:\/\/machineryequipmentonline.com\/video-equipment\/uncategorized\/magnetic-tape-recordingmagnetic-tape-basics\/"},"modified":"2015-09-03T15:10:00","modified_gmt":"2015-09-03T15:10:00","slug":"magnetic-tape-recordingmagnetic-tape-basics","status":"publish","type":"post","link":"http:\/\/machineryequipmentonline.com\/video-equipment\/magnetic-tape-recordingmagnetic-tape-basics\/","title":{"rendered":"Magnetic tape recording:Magnetic tape basics"},"content":{"rendered":"<div class=\"izlds6a0dc9212a5d0\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '61e5902552e2353963d8d2f1bd1f4a8f',\n\t\t'format' : 'iframe',\n\t\t'height' : 250,\n\t\t'width' : 300,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/61e5902552e2353963d8d2f1bd1f4a8f\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.izlds6a0dc9212a5d0 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.izlds6a0dc9212a5d0 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.izlds6a0dc9212a5d0 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.izlds6a0dc9212a5d0 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.izlds6a0dc9212a5d0 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<h3 align=\"justify\">Magnetic tape basics<\/h3>\n<p align=\"justify\">All magnetic materials, video tape coatings amongst them, may be regarded for practical purposes as consisting of an infinite number of tiny bar magnets, each with its own north and south poles. This is a simplification, but suits our purposes well. In the natural state, these bar magnets are randomly aligned within the material so that their fields cancel one another out, and no external magnetic force is present. To magnetise the material, be it a blank tape or a solenoid core, we have to apply an exter- nal magnetic force to align the internal magnets so that they sit parallel to one another, with all their N poles pointing in the same direction. When  <\/p>\n<p align=\"justify\"><a href=\"http:\/\/lh3.googleusercontent.com\/-dWwFCxKxIOY\/VehiK7XaSOI\/AAAAAAAB7MQ\/tFnQRk72Zk8\/s1600-h\/Television-and-Video-Technology-0142%25255B2%25255D.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-right-width: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px; padding-top: 0px\" title=\"Television and Video Technology-0142\" border=\"0\" alt=\"Television and Video Technology-0142\" src=\"http:\/\/lh3.googleusercontent.com\/-8zcE-QHVdK8\/VehicDSm09I\/AAAAAAAB7Mg\/HEKzQrMSSbA\/Television-and-Video-Technology-0142.jpg?imgmax=800\" width=\"307\" height=\"249\" \/><\/a>  <\/p>\n<p align=\"justify\">the external field is removed, most of the magnets remain in alignment and the material now exhibits magnetic properties of its own.  <\/p>\n<p align=\"justify\">The relationship or transfer curve (Figure 21.2) between the external force and the retained magnetism on the tape is not linear. The transfer curve is a graph with the <i>magnetising force <\/i>(<i>H<\/i>) plotted along the horizontal axis, and the stored <i>flux density <\/i>(<i>B<\/i>) on the vertical axis. Our starting point is in the centre, point 0. Here, no external magnetising force is present, and the magnetic material\u2019s internal magnets are lying in random fashion\u2014 hence zero stored flux. Let\u2019s suppose we now apply a linearly increasing external flux. The flux density (strength of magnetism) in the material would increase in a non-linear fashion as shown by the curve 0\u2013T. At point T, the material has reached magnetic saturation and all its internal mag- nets are rigidly aligned with each other\u2014no increase in applied magnetic force will have any effect. If we now remove the magnetising force, bring- ing the <i>H <\/i>coordinate back to zero, we see that a lot of magnetism is retained by the specimen, represented by point U. This is the remanence of the material, the \u2018stored charge\u2019 as it were. For recording tape, it needs to be as high as possible.  <\/p><div class=\"bykcr6a0dc9212a701\" ><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-0778475562755157\"\n     crossorigin=\"anonymous\"><\/script>\n<!-- 300x600 television-and-video -->\n<ins class=\"adsbygoogle\"\n     style=\"display:inline-block;width:300px;height:600px\"\n     data-ad-client=\"ca-pub-0778475562755157\"\n     data-ad-slot=\"6549443290\"><\/ins>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.bykcr6a0dc9212a701 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.bykcr6a0dc9212a701 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.bykcr6a0dc9212a701 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.bykcr6a0dc9212a701 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.bykcr6a0dc9212a701 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<div class=\"emjps6a0dc9212a67b\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '0c1eb4c533eaedb7b996f49a5a4983a9',\n\t\t'format' : 'iframe',\n\t\t'height' : 300,\n\t\t'width' : 160,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/0c1eb4c533eaedb7b996f49a5a4983a9\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.emjps6a0dc9212a67b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.emjps6a0dc9212a67b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.emjps6a0dc9212a67b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.emjps6a0dc9212a67b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.emjps6a0dc9212a67b {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n\n<p align=\"justify\">Figure 21.3 is an expansion of Figure 21.2 to take in all four quadrants. We left the material at point U with a stored flux. To remove the flux and demagnetise the tape material, it is necessary to apply a negative mag- netising force, represented by 0\u2013V, whereupon stored flux <i>B <\/i>returns to zero. Further negative applied force (V\u2013W) pushes the stored flux to satu- ration point in the opposite direction, so that all the magnets in the tape  <\/p>\n<p align=\"justify\"><a href=\"http:\/\/lh3.googleusercontent.com\/-sgNJ0TUrv1w\/Vehit9l_PgI\/AAAAAAAB7Mw\/pC7lZl0cd-8\/s1600-h\/Television-and-Video-Technology-0143.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-right-width: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px; padding-top: 0px\" title=\"Television and Video Technology-0143\" border=\"0\" alt=\"Television and Video Technology-0143\" src=\"http:\/\/lh3.googleusercontent.com\/-jgU7IWS5E1Q\/VehiyBMNU_I\/AAAAAAAB7NM\/wqt5ga54sCk\/Television-and-Video-Technology-0143%25255B2%25255D.jpg?imgmax=800\" width=\"305\" height=\"282\" \/><\/a>  <\/p>\n<p align=\"justify\">are once again aligned, but all pointing the other way, represented by point X. Removal of the applied force takes us back to the remanence point, this time in the negative direction \u2013 point Y. To demagnetise the tape, a positive applied force 0\u2013Z is required, an increase of which will again reverse the stored flux to reach saturation once more at point T. The diagram is called a magnetising <i>hysteresis curve <\/i>and one cycle of an applied magnetising waveform takes us right round it. It can now be seen how the \u2018degaussing\u2019 or erasing process works. Here, we apply a large alternating magnetic field sufficient to drive the material to saturation in both direc- tions. The field is then allowed to decay linearly to zero, creating smaller and smaller hysteresis loops until they disappear into a dot at point 0, and the material is fully demagnetised.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Magnetic tape basics All magnetic materials, video tape coatings amongst them, may be regarded for practical purposes as consisting of an infinite number of tiny bar magnets, each with its own north and south poles. This is a simplification, but suits our purposes well. In the natural state, these bar magnets are randomly aligned within [&hellip;]<br \/><a href=\"http:\/\/machineryequipmentonline.com\/video-equipment\/magnetic-tape-recordingmagnetic-tape-basics\/\" class=\"more-link\" >Continue reading&#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"aioseo_notices":[],"views":744,"_links":{"self":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/99"}],"collection":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/comments?post=99"}],"version-history":[{"count":0,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/99\/revisions"}],"wp:attachment":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/media?parent=99"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/categories?post=99"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/tags?post=99"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}