{"id":212,"date":"2026-03-05T03:46:33","date_gmt":"2026-03-05T03:46:33","guid":{"rendered":"https:\/\/ai7sg.com\/?p=212"},"modified":"2026-03-05T03:46:33","modified_gmt":"2026-03-05T03:46:33","slug":"2-meter-df-board","status":"publish","type":"post","link":"https:\/\/ai7sg.com\/index.php\/2026\/03\/05\/2-meter-df-board\/","title":{"rendered":"2 meter DF board"},"content":{"rendered":"\n<p>There was a delay getting my 20 meter polar modulation prototype back, so I decided to design a 2-channel phase coherent direction finding system for 2 meters.<br>I decided to see just how inexpensively I could do it. The answer kind of surprised me. $4.51 in parts, plus my trusty Pico2!<br>I wasn&#8217;t about to build it like that. It was a pretty bad design. But there was room to triple my BOM and make it decent. So that&#8217;s what I did.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"789\" height=\"785\" src=\"https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-schematics.png\" alt=\"\" class=\"wp-image-215\" srcset=\"https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-schematics.png 789w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-schematics-300x298.png 300w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-schematics-150x150.png 150w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-schematics-768x764.png 768w\" sizes=\"auto, (max-width: 789px) 100vw, 789px\" \/><\/figure>\n\n\n\n<p>SMA inputs. ESD \/ RF limiter. Band pass filter to reject FM &amp; TV. RF preamps. Dual conversion superhet design. Nice temperature-stable transistor amplifiers, high linearity mixers, and clean power. Crappy ADC though (using the Pico 2&#8217;s onboard ADC), but the right amount of gain for it to optimize dynamic range &amp; sensitivity.<br><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"423\" src=\"https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-front-1024x423.png\" alt=\"\" class=\"wp-image-214\" srcset=\"https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-front-1024x423.png 1024w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-front-300x124.png 300w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-front-768x317.png 768w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-front.png 1050w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"420\" src=\"https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-back-1024x420.png\" alt=\"\" class=\"wp-image-213\" srcset=\"https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-back-1024x420.png 1024w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-back-300x123.png 300w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-back-768x315.png 768w, https:\/\/ai7sg.com\/wp-content\/uploads\/2026\/03\/DF2m-back.png 1049w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p>Just ordered them! Hopefully I&#8217;ll have time to write the software and build the antenna before the next fox hunt!<\/p>\n","protected":false},"excerpt":{"rendered":"<p>There was a delay getting my 20 meter polar modulation prototype back, so I decided to design a 2-channel phase coherent direction finding system for 2 meters.I decided to see just how inexpensively I could do it. The answer kind of surprised me. $4.51 in parts, plus my trusty Pico2!I wasn&#8217;t about to build it [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":215,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-212","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/posts\/212","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/comments?post=212"}],"version-history":[{"count":1,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/posts\/212\/revisions"}],"predecessor-version":[{"id":216,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/posts\/212\/revisions\/216"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/media\/215"}],"wp:attachment":[{"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/media?parent=212"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/categories?post=212"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ai7sg.com\/index.php\/wp-json\/wp\/v2\/tags?post=212"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}