{"id":196,"date":"2017-08-11T21:20:57","date_gmt":"2017-08-11T21:20:57","guid":{"rendered":"https:\/\/geekblog.febo.com\/wp\/?p=196"},"modified":"2025-09-26T23:48:27","modified_gmt":"2025-09-26T23:48:27","slug":"fts-4100-cesium-standard-tests","status":"publish","type":"post","link":"https:\/\/blog.febo.com\/?p=196","title":{"rendered":"FTS-4100 Cesium Standard tests"},"content":{"rendered":"<p>It wasn&#8217;t too hard for the <a href=\"http:\/\/hamsci.org\">HamSci<\/a> guys to convince me to bring a Cesium frequency standard to my portable location in Michigan to drive the HPSDR receiver that will do band recordings for the <a href=\"http:\/\/hamsci.org\/basic-project\/2017-total-solar-eclipse\">2017 Total Solar Eclipse<\/a> <a href=\"http:\/\/hamsci.org\/2017-eclipse-hf-wideband-recording-experiment\">HF Wideband Recording Experiment<\/a>. I had been planning to use a GPSDO, but that would be too simple.<\/p>\n<p>My \u201csort-of-portable\u201d Cesium is an old FTS-4100 that came out of military service. It was designed for shipboard use (I think as part of crypto systems) and there\u2019s not a lot of information available online about it. When I went digging, most of the technical threads I found were buried among unrelated searches, even odd detours into policy discussions on <a href=\"https:\/\/readwrite.com\/gambling\/betting\/utah\/\">sports betting in Utah<\/a>. The unit itself weighs probably 25 pounds and is just a white box with a big heatsink and tiny control box bolted to the front. It has two 5 MHz outputs. Just to verify that it\u2019s still working after several years in standby mode, I powered it up this week and did comparisons with an HP 5071A cesium to check on the frequency offset, and also with a quartz BVA oscillator to look at the short-term performance.<\/p>\n<p>Bottom line: this thing works really well. It&#8217;s frequency is within 1e<sup>-12<\/sup> compared to the 5071A, and its short term noise may be the best of any of my Cesiums; that&#8217;s a good thing for this radio experiment. Plots below.<\/p>\n<p><a href=\"http:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-hp5071a_08-11-17_freq.png\" data-rel=\"penci-gallery-image-content\" ><img decoding=\"async\" class=\"aligncenter size-medium wp-image-198\" src=\"http:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-hp5071a_08-11-17_freq-300x168.png\" alt=\"fts4100-hp5071a_08-11-17_freq\" width=\"300\" height=\"168\" srcset=\"https:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-hp5071a_08-11-17_freq-300x168.png 300w, https:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-hp5071a_08-11-17_freq-1024x574.png 1024w, https:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-hp5071a_08-11-17_freq.png 1280w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p><a href=\"http:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-08-11-17_combined_adev.png\" data-rel=\"penci-gallery-image-content\" ><img decoding=\"async\" class=\"aligncenter size-medium wp-image-197\" src=\"http:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-08-11-17_combined_adev-300x168.png\" alt=\"fts4100-08-11-17_combined_adev\" width=\"300\" height=\"168\" srcset=\"https:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-08-11-17_combined_adev-300x168.png 300w, https:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-08-11-17_combined_adev-1024x574.png 1024w, https:\/\/blog.febo.com\/wp-content\/uploads\/2017\/08\/fts4100-08-11-17_combined_adev.png 1280w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>It wasn&#8217;t too hard for the HamSci guys to convince me to bring a Cesium frequency standard to my portable location in Michigan to drive the HPSDR receiver that will&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"no","_lmt_disable":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[4,9,7,2],"tags":[22,23,24],"class_list":["post-196","post","type-post","status-publish","format-standard","hentry","category-ham-radio","category-sdr","category-test-and-lab-equipment","category-time-and-frequency","tag-cesium","tag-frequency-standard","tag-time-and-frequency"],"_links":{"self":[{"href":"https:\/\/blog.febo.com\/index.php?rest_route=\/wp\/v2\/posts\/196","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.febo.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.febo.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.febo.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.febo.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=196"}],"version-history":[{"count":5,"href":"https:\/\/blog.febo.com\/index.php?rest_route=\/wp\/v2\/posts\/196\/revisions"}],"predecessor-version":[{"id":1316,"href":"https:\/\/blog.febo.com\/index.php?rest_route=\/wp\/v2\/posts\/196\/revisions\/1316"}],"wp:attachment":[{"href":"https:\/\/blog.febo.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=196"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.febo.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=196"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.febo.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=196"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}