{"id":1087,"date":"2017-11-13T18:44:02","date_gmt":"2017-11-13T17:44:02","guid":{"rendered":"http:\/\/www.sm0brf.se\/?p=1087"},"modified":"2017-11-13T22:30:03","modified_gmt":"2017-11-13T21:30:03","slug":"common-mode-measurement-of-dl1000-telephone-line","status":"publish","type":"post","link":"https:\/\/www.sm0brf.se\/?p=1087","title":{"rendered":"Common mode measurement of DL1000 telephone cable."},"content":{"rendered":"<p>I&#8217;ve been a bit sceptical about the balance of the military telephone cable called DL1000 in Sweden. It almost looks as if one wire is wound around the other rather than two twisted wires. So I made a measurement as outlined in the sketch below while listening on strong signals:<\/p>\n<p><a href=\"https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-1086\" src=\"https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001-300x129.jpg\" alt=\"\" width=\"300\" height=\"129\" srcset=\"https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001-300x129.jpg 300w, https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001-768x331.jpg 768w, https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001-1024x442.jpg 1024w, https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001-624x269.jpg 624w, https:\/\/www.sm0brf.se\/wp-content\/uploads\/2017\/11\/Common-mode-measurement-DL1000-001.jpg 1481w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p>As reference I connected both wires in parallel connected directly to the measurement receiver.<\/p>\n<p>The results were:<\/p>\n<p>Frequency\u00a0\u00a0\u00a0\u00a0 Common mode rejection<\/p>\n<p>7 MHz\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 25 dB<\/p>\n<p>3.5 MHz\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 40 dB<\/p>\n<p>There was no difference with and without the load resistor R.<\/p>\n<p>So the telephone line is OK as a feeder for receiving antennas on 80 and below as regards to common mode pick up but doubtful on 40m.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I&#8217;ve been a bit sceptical about the balance of the military telephone cable called DL1000 in Sweden. It almost looks as if one wire is wound around the other rather than two twisted wires. So I made a measurement as outlined in the sketch below while listening on strong signals: As reference I connected both [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[],"class_list":["post-1087","post","type-post","status-publish","format-standard","hentry","category-okategoriserade-en"],"_links":{"self":[{"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=\/wp\/v2\/posts\/1087","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1087"}],"version-history":[{"count":4,"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=\/wp\/v2\/posts\/1087\/revisions"}],"predecessor-version":[{"id":1095,"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=\/wp\/v2\/posts\/1087\/revisions\/1095"}],"wp:attachment":[{"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1087"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1087"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sm0brf.se\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1087"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}