{"id":370,"date":"2009-03-29T19:00:19","date_gmt":"2009-03-29T17:00:19","guid":{"rendered":"http:\/\/pa3hcm.utreg.net\/?p=370"},"modified":"2021-01-18T20:18:16","modified_gmt":"2021-01-18T19:18:16","slug":"370","status":"publish","type":"post","link":"https:\/\/www.pa3hcm.nl\/?p=370","title":{"rendered":"DK7ZB yagi for 144MHz"},"content":{"rendered":"\n

Introduction<\/h2>\n\n\n\n
\"The<\/a>
My DK7ZB yagi for 144MHz<\/figcaption><\/figure><\/div>\n\n\n\n

After the somewhat disapointing results of the DJ9BV antenna, I decided to try another model. This time I selected a 9 element DK7ZB for my test. I already bought some square alu bars, each 250cm tall. Since the 9 element DK7ZB is 5 meters tall, this should fit perfectly.<\/p>\n\n\n\n

Click here<\/a> to visit DK7ZB’s homepage, including all his antenna designs and lots of references.<\/p>\n\n\n\n\n\n\n\n

Construction<\/h2>\n\n\n\n

This is my initial sizing, all sizes in mm:<\/p>\n\n\n\n

Element<\/strong><\/td>Distance to reflector<\/strong><\/td>Length<\/strong><\/td>Diameter<\/strong><\/td><\/tr>
Reflector<\/td>(0)<\/td>1029<\/td>6<\/td><\/tr>
Dipole<\/td>345<\/td>(?)<\/td>10<\/td><\/tr>
Director 1<\/td>615<\/td>958<\/td>6<\/td><\/tr>
Director 2<\/td>1175<\/td>930<\/td>6<\/td><\/tr>
Director 3<\/td>1870<\/td>915<\/td>6<\/td><\/tr>
Director 4<\/td>2675<\/td>904<\/td>6<\/td><\/tr>
Director 5<\/td>3505<\/td>897<\/td>6<\/td><\/tr>
Director 6<\/td>4345<\/td>913<\/td>6<\/td><\/tr>
Director 7<\/td>4980<\/td>895<\/td>6<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The sizing corresponds to DK7ZB, except for the element length. I decided NOT to isolate the elements, so the length has to be extended with 5mm (when using a 20mm boom).<\/p>\n\n\n\n

\"boom-constructie\"<\/a><\/figure><\/div>\n\n\n\n

The picture above shows 3 bars, each 2500mm. The bars are bolted together according to the above picture. The middle section is just a small part of another bar. A hole is drilled through the three bars. A 70mm bolt is then put into the hole and closed with a wing nut. Apply wide washers on both ends of the bolt connection to get a more solid construction.<\/p>\n\n\n\n

\"element-bevestiging\"<\/a><\/figure><\/div>\n\n\n\n

The picture above shows the way each element is mounted through the boom. A hole is drilled at both sides which will hold the element. A smaller second hole is drilled in the top side of the bar, to fit a self-drilling screw.<\/p>\n\n\n\n

Progress<\/h2>\n\n\n\n

March 14th, 2009<\/b> At the yearly radiomarket in Rosmalen I bought a couple of prefab folded dipoles, including balun (1\/2 wave coax) and N-connector. I decided to use these for the DK7ZB.<\/p>\n\n\n\n

March 22nd, 2009<\/b> I started with the building activities. I drilled all the bars and mounted the reflector, dipole and 3 directors. Unfortunately I didn’t have enough aluminium to create the final 4 bars. I used 6mm alu for the reflector and directors. These are mounted through the boom (not isolated). Therefore I increased the length of each element with 5mm to compensate the shortening of the middle 2cm’s by the bar.<\/p>\n\n\n\n

March 25th, 2009<\/b> I bought some stainless bolts and washers to connect the bars. Unfortunately stainless wing nuts where not available, so I bought “normal” wings.<\/p>\n\n\n\n

March 29th, 2009<\/b> I finished the antenna and did some first measurements. The antenna resonates at 146MHz, which is too high. I would like to have it resonating at 144.3 MHz. The high resonance frequency is probably caused by the prefab dipole, so I might replace it in the future. However, the SWR on 144.3 is 1.5 which is not bad.<\/p>\n\n\n\n

The gain seems to be ok, and the sidelobs are quite surpressed. F\/B ratio is ok too. There is a very sharp dip on both sides (at 90 and 270 degrees). For more serious measurements I have to put it in my antenna post, but that one is still under construction…<\/p>\n\n\n\n

  • \"[image]\"<\/figure><\/li>
  • \"[image]\"<\/figure><\/li>
  • \"[image]\"<\/figure><\/li><\/ul><\/figure>\n","protected":false},"excerpt":{"rendered":"

    Introduction After the somewhat disapointing results of the DJ9BV antenna, I decided to try another model. This time I selected a 9 element DK7ZB for my test. I already bought some square alu bars, each 250cm tall. Since the 9 element DK7ZB is 5 meters tall, this should fit perfectly. Click here to visit DK7ZB’s […]<\/p>\n","protected":false},"author":1,"featured_media":374,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[33,34,32],"class_list":["post-370","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-antennas","tag-2m","tag-antenna","tag-yagi"],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":6}},"_links":{"self":[{"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/posts\/370","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=370"}],"version-history":[{"count":10,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/posts\/370\/revisions"}],"predecessor-version":[{"id":1959,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/posts\/370\/revisions\/1959"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=\/wp\/v2\/media\/374"}],"wp:attachment":[{"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=370"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=370"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.pa3hcm.nl\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=370"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}