{"id":3213,"date":"2014-03-12T10:04:00","date_gmt":"2014-03-11T23:04:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2014\/03\/12\/direct-conversion-receivers-af-transformers-and-motorboating\/"},"modified":"2025-07-21T14:44:41","modified_gmt":"2025-07-21T04:44:41","slug":"direct-conversion-receivers-af-transformers-and-motorboating","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2014\/03\/12\/direct-conversion-receivers-af-transformers-and-motorboating\/","title":{"rendered":"Direct Conversion Receivers, AF Transformers, and Motorboating"},"content":{"rendered":"<div class=\"separator\" style=\"clear: both; text-align: center;\"> <a href=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2014\/03\/HerringAidJoke.png\" imageanchor=\"1\" style=\"margin-left: 1em; margin-right: 1em;\"><img loading=\"lazy\" decoding=\"async\" border=\"0\" src=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2014\/03\/HerringAidJoke.png\" height=\"400\" width=\"258\" \/><\/a><\/div>\n<p> <strong>The Herring Aid 5 is a direct conversion receiver (scroll down for details). It is a minimalist design from 1976 using parts available at Radio Shack stores. One of the parts no longer carried by Radio Shack is a 10K-2K ohm audio transformer. Following NORCAL&#8217;s 1998 design update I ordered an equivalent Mouser part (Xicon 42TU002-RC). I had been running the receiver with simple RC coupling instead of the transformer.<\/strong><br \/> <strong><\/strong><br \/> <strong>Yesterday the Mouser part arrived and I put it into the circuit. An increase in AF gain was immediately apparent, but the thing went into AF oscillation as soon as I turned up the AF gain. <\/strong><br \/> <strong><\/strong><br \/> <strong>I tried beefing up the AF decoupling. But I think the real problem is just the presence in the middle of the board of a rather large (1 inch x 1 inch) audio transformer. I moved it around a bit to get it away from the toroid of the preceding stage. This helped a bit, but it still breaks into oscillation if I turn up the AF gain. <\/strong><br \/> <strong><\/strong><br \/> <strong>Any suggestions? Or is this just part of the minimalist 1976 lifestyle?<\/strong> <\/p>\n<p> Our book: &#8220;SolderSmoke &#8212; Global Adventures in Wireless Electronics&#8221; <a href=\"http:\/\/soldersmoke.com\/book.htm\">http:\/\/soldersmoke.com\/book.htm<\/a> Our coffee mugs, T-Shirts, bumper stickers: <a href=\"http:\/\/www.cafepress.com\/SolderSmoke\">http:\/\/www.cafepress.com\/SolderSmoke<\/a> Our Book Store: <a href=\"http:\/\/astore.amazon.com\/contracross-20\">http:\/\/astore.amazon.com\/contracross-20<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>The Herring Aid 5 is a direct conversion receiver (scroll down for details). It is a minimalist design from 1976 using parts available at Radio Shack stores. One of the parts no longer carried by Radio Shack is a 10K-2K ohm audio transformer. Following NORCAL&#8217;s 1998 design update I ordered an equivalent Mouser part (Xicon &hellip; <a href=\"https:\/\/www.homebrewradio.us\/blog\/2014\/03\/12\/direct-conversion-receivers-af-transformers-and-motorboating\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Direct Conversion Receivers, AF Transformers, and Motorboating&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":3214,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[167,85,25],"tags":[],"class_list":["post-3213","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-herring-aid-5","category-minimalist-radio","category-troubleshooting"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/3213","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=3213"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/3213\/revisions"}],"predecessor-version":[{"id":3215,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/3213\/revisions\/3215"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/3214"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=3213"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=3213"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=3213"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}