{"id":36,"date":"2018-10-21T15:13:44","date_gmt":"2018-10-21T15:13:44","guid":{"rendered":"https:\/\/fletch.scot\/wp\/?p=36"},"modified":"2020-09-20T10:48:15","modified_gmt":"2020-09-20T10:48:15","slug":"2m-omni-directional-aerial","status":"publish","type":"post","link":"https:\/\/fletch.scot\/wp\/?p=36","title":{"rendered":"2m Omni-directional Aerial"},"content":{"rendered":"

I thought it was about time I understood aerials more, so I am building an omnidirectional aerial for LEO<\/a> satellite use.<\/p>\n

I\u2019m hopeful that I will be able to use the aerial in my attic, but if not I\u2019ll use it in the garden. The aerial I\u2019ve picked is documented in the ARRL Antenna Book<\/em> in one of the supplementary PDFs. The article which describes it was published in QST in 2001 and is called \u201cA Simple Fixed Antenna for VHF\/UHF Satellite Work\u201d by L. B. Cebik, W4RNL. I can\u2019t link to it because it is copyrighted by ARRL but I explain most of it below. It is a pair of Moxon<\/a> rectangles at 90\u00b0 to each other.<\/p>\n

I made a model of the aerial in the excellent Mac application cocoaNEC<\/a> by Kok Chen, W7AY. The other aerial modelling applications I looked at were all based on spreadsheet tables. I found the programming approach used by cocoaNEC easier to use. Here\u2019s the shape of the aerial as shown by cocoaNEC.<\/p>\n

\"\"
Cebik Geometry<\/figcaption><\/figure>\n

\u00a0<\/p>\n

The driven elements are the top ones, and the reflectors are the bottom ones. Both have vertical parts which make up the Moxon rectangles. One of the driven elements is driven from the feeder through a matching line. The other driven element is driven 90\u00b0 out of phase through a phasing line. This gives the radiation pattern below. This is the VHF version of the aerial. As you can see it is almost omnidirectional but favours elevations that you might expect to be able to use a satellite at.<\/p>\n

\"\"<\/figure>\n

Cebik Radiation Pattern<\/p>\n

\u00a0<\/p>\n

This was output by this cocoaNEC program<\/a> of the Cebik aerial.


<\/pre>\n","protected":false},"excerpt":{"rendered":"
I thought it was about time I understood aerials more, so I am building an omnidirectional aerial for LEO satellite use. I\u2019m hopeful that I will be able to use the aerial in my attic, but if not I\u2019ll use it in the garden. The aerial I\u2019ve picked is documented in the ARRL Antenna Book … <\/p>\n
Continue reading “2m Omni-directional Aerial”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[6],"class_list":["post-36","post","type-post","status-publish","format-standard","hentry","category-aerial","tag-aerial"],"_links":{"self":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/36","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=36"}],"version-history":[{"count":6,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/36\/revisions"}],"predecessor-version":[{"id":220,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/36\/revisions\/220"}],"wp:attachment":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=36"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=36"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=36"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}