{"id":2842,"date":"2015-05-17T21:12:45","date_gmt":"2015-05-17T20:12:45","guid":{"rendered":"http:\/\/lefars.org.uk\/WPblog\/?p=2842"},"modified":"2015-05-18T09:07:16","modified_gmt":"2015-05-18T08:07:16","slug":"homebrew-21-mhz-4e-beam-part-1","status":"publish","type":"post","link":"https:\/\/lefars.org.uk\/WPblog\/homebrew-21-mhz-4e-beam-part-1\/","title":{"rendered":"Homebrew 21 MHz 4e Beam Part #1"},"content":{"rendered":"

Months ago I ordered some aluminium in preparation for another antenna project. \u00a0Wtih the assistance of John M0UKD the plan was to build a 21 MHz 4E Yagi. The aluminium was ordered from\u00a0aluminium warehouse<\/a>, and cost around \u00a3100 including delivery.<\/p>\n

\"WM_20150504_190640\"\u00a0 \u00a0\"WM_20150504_191110\"<\/p>\n

The on-line shop provides and delivers lengths of up to 5 meters, and they have a vast selection of grades and lengths available.<\/p>\n

The design was by DK7ZB<\/a>\u00a0and was chosen because of the short boom length and high gain. The boom is 5 meters, and made from 40mm box split into 2 x 2.5m. \u00a0The reflector is 7.2 meters long and director 2 is 6.4 meters long (to give you some scale) You will find all the measurements, VSWR and gain data on Martin\u2019s very extensive website.<\/p>\n

The antenna construction involves sections of the elements telescoping into each other, and Martin points out this is a critical part of the design. The aluminium was ordered with this in mind, and while some sections required no adjustment others didnt quite go to plan. We needed to \u201cgrind\u201d some of the sections just a little, to ensure they would fit and telescope correctly. This part of the construction required 1 complete grinding disc and around 2 Hrs. work !<\/p>\n

\"WM_P1010119\"<\/p>\n

Once each section that required attention was ground down, the elements were mounted on the boom. I used various places to source all the parts<\/a> but some on-line resources<\/a>\u00a0have been linked.<\/p>\n

As with any home construction project you always get some unexpected challenges, the first was how to get the elements to lay flat on the plastic formers. The former needs to be mounted to the boom by a nut, and this isnt easy to recess, meaning we had to cut a small hole to locate the nut into the element, allowing the element to lay flat.<\/p>\n

\"WM_P1010125\"<\/p>\n

With this type of beam it presents 28? (by design) and so requires a coax matching section<\/a>.\u00a0This is yet to be constructed, but the final build phase will include this and mounting the driven element.<\/p>\n

You can see the progress so far, and further updates and pictures will be posted once tested.<\/p>\n

73 Dave M0TAZ
\n<\/a>\u00a0\u00a0\u00a0\"WM_20150504_185439\"<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Months ago I ordered some aluminium in preparation for another antenna project. \u00a0Wtih the assistance of John M0UKD the plan was to build a 21 MHz 4E Yagi. The aluminium was ordered from\u00a0aluminium warehouse, and cost around \u00a3100 including delivery. … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":14,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"gallery","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[43,7],"tags":[101,103,82,72,102,83],"class_list":["post-2842","post","type-post","status-publish","format-gallery","hentry","category-antennas","category-portable","tag-21mhz","tag-aerial","tag-beam","tag-hf","tag-homebrew","tag-yagi","post_format-post-format-gallery"],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p22sia-JQ","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts\/2842","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/users\/14"}],"replies":[{"embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/comments?post=2842"}],"version-history":[{"count":4,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts\/2842\/revisions"}],"predecessor-version":[{"id":2857,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/posts\/2842\/revisions\/2857"}],"wp:attachment":[{"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/media?parent=2842"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/categories?post=2842"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lefars.org.uk\/WPblog\/wp-json\/wp\/v2\/tags?post=2842"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}