{"id":6120,"date":"2022-11-09T12:57:00","date_gmt":"2022-11-09T01:57:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2022\/11\/09\/direct-conversion-receiver-simple-2-diode-mixer-defeats-radio-marti-but-diode-ring-is-the-best\/"},"modified":"2025-07-22T18:02:55","modified_gmt":"2025-07-22T08:02:55","slug":"direct-conversion-receiver-simple-2-diode-mixer-defeats-radio-marti-but-diode-ring-is-the-best","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2022\/11\/09\/direct-conversion-receiver-simple-2-diode-mixer-defeats-radio-marti-but-diode-ring-is-the-best\/","title":{"rendered":"Direct Conversion Receiver &#8212; Simple 2-Diode Mixer Defeats Radio Marti, but Diode Ring is the Best"},"content":{"rendered":"<p><iframe loading=\"lazy\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen=\"\" frameborder=\"0\" height=\"247\" src=\"https:\/\/www.youtube.com\/embed\/a1HjUOsWhmI?rel=0\" title=\"YouTube video player\" width=\"440\"><\/iframe><\/p>\n<p> <span face=\"Roboto, Arial, sans-serif\" style=\"background-color: rgba(0, 0, 0, 0.05); color: #0f0f0f; font-size: 14px; white-space: pre-wrap;\">Here is another update on Direct Conversion receiver construction. In Northern Virginia we get very strong signals from the Radio Marti transmitter in Greenville NC. During the morning hours it is just above the 40 meter band at 7335 kHz. In the evening it is a bit higher in frequency at 7435 KHz. (in the video above I mistakenly give the morning frequency, when in fact they were on the higher evening frequency). In either case, Radio Marti has been a big source of unwanted AM breakthrough in our simple DC receivers. It now serves as something of a test of our bandpass filters and mixers. <\/span><\/p>\n<p><span class=\"style-scope yt-formatted-string\" dir=\"auto\" face=\"Roboto, Arial, sans-serif\" style=\"background: rgba(0, 0, 0, 0.05); border: 0px; color: #0f0f0f; font-size: 14px; margin: 0px; padding: 0px; white-space: pre-wrap;\">In this video I try out the simple mixer described in detail here: <\/span><a class=\"yt-simple-endpoint style-scope yt-formatted-string\" dir=\"auto\" href=\"https:\/\/www.youtube.com\/redirect?event=video_description&#038;redir_token=QUFFLUhqbTFBUFpqOG01RUgxVGh4ZHl2QWJCR2JjN0ZNd3xBQ3Jtc0ttZ3J0SXJ6WlZ0QTAxcHV5UmtQQ2xhYlV6bkNvdkRsOXFPLUxCdG1rUU8ya2tIX0VnVG8yTnhqLWVjLUtQYUFlMmdxTVphTm43SVJEekFSS1BxZmhid293dmNZZFZFNF9lNkRBdGFfc3otbTAzM3hvUQ&#038;q=https%3A%2F%2Fsoldersmoke.blogspot.com%2F2022%2F11%2Funderstanding-very-simple-two-diode.html&#038;v=a1HjUOsWhmI\" rel=\"nofollow\" spellcheck=\"false\" style=\"background-color: rgba(0, 0, 0, 0.05); cursor: pointer; display: var(--yt-endpoint-display,inline-block); font-family: Roboto, Arial, sans-serif; font-size: 14px; overflow-wrap: var(--yt-endpoint-word-wrap,none); text-decoration: var(--yt-endpoint-text-regular-decoration,none); white-space: pre-wrap; word-break: var(--yt-endpoint-word-break,none);\" target=\"_blank\">https:\/\/soldersmoke.blogspot.com\/2022&#8230;<\/a><\/p>\n<p><span face=\"Roboto, Arial, sans-serif\" style=\"color: #0f0f0f;\"><span style=\"background-color: rgba(0, 0, 0, 0.05); font-size: 14px; white-space: pre-wrap;\">The following morning, I tested the mixer with Radio Marti (in fact) on 7335 kHz. By adjusting the VFO signal input to the minimum value needed to turn on the diodes, I was able to bring Radio Marti AM breakthrough to minimal levels. But I could still hear it (weakly) in the background. Putting a very simple diplexer at the audio output of the mixer (just a .1uF capacitor in series with a 47 ohm resistor to ground) helped a lot. <\/span><\/span><\/p>\n<p><span face=\"Roboto, Arial, sans-serif\" style=\"background-color: rgba(0, 0, 0, 0.05); color: #0f0f0f; font-size: 14px; white-space: pre-wrap;\">I could also hear break through from Spanish-language broadcasts from Vatican Radio on 7305 kHz (using the 250 kW transmitter in Greenville NC) from 11:30-11:45. Perhaps most surprisingly, I was also getting AM breakthrough from 40 meter FT8! <\/span><\/p>\n<p><span face=\"Roboto, Arial, sans-serif\" style=\"background-color: rgba(0, 0, 0, 0.05); color: #0f0f0f; font-size: 14px; white-space: pre-wrap;\">Here is a short video showing the simple two-diode mixer in action during the morning hours:<\/span><\/p>\n<p><span face=\"Roboto, Arial, sans-serif\" style=\"background-color: rgba(0, 0, 0, 0.05); color: #0f0f0f; font-size: 14px; white-space: pre-wrap;\"> <iframe loading=\"lazy\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen=\"\" frameborder=\"0\" height=\"247\" src=\"https:\/\/www.youtube.com\/embed\/rkXViMjjwjo?rel=0\" title=\"YouTube video player\" width=\"440\"><\/iframe> <\/span><\/p>\n<p><span style=\"background-color: rgba(0, 0, 0, 0.05); color: #0f0f0f; font-size: 14px; white-space: pre-wrap;\">I also tried out the more common two diode mixer with trifilar toroid. (In this one, the VFO turns both diodes on, then turns both of them off). The results were similar to what I got with the other two diode mixer. <\/span><\/p>\n<p><span class=\"style-scope yt-formatted-string\" dir=\"auto\" face=\"Roboto, Arial, sans-serif\" style=\"background: rgba(0, 0, 0, 0.05); border: 0px; color: #0f0f0f; font-size: 14px; margin: 0px; padding: 0px; white-space: pre-wrap;\">We are trying to develop four circuits &#8212; bandpass filter, mixer, variable frequency oscillator, and audio amplifier &#8212; that will be simple enough for construction by high school students, but not so simple as to compromise performance. We want the receiver to work well. <\/span><\/p>\n<div><span class=\"style-scope yt-formatted-string\" dir=\"auto\" face=\"Roboto, Arial, sans-serif\" style=\"background: rgba(0, 0, 0, 0.05); border: 0px; color: #0f0f0f; font-size: 14px; margin: 0px; padding: 0px; white-space: pre-wrap;\"><br \/><\/span><\/div>\n<div><span class=\"style-scope yt-formatted-string\" dir=\"auto\" face=\"Roboto, Arial, sans-serif\" style=\"background: rgba(0, 0, 0, 0.05); border: 0px; color: #0f0f0f; font-size: 14px; margin: 0px; padding: 0px; white-space: pre-wrap;\">So far, my conclusion is that the best results come from the diode rig mixer with two trifilar toroids. Here is a short video showing the diode ring in action on the morning of November 9, 2022:<\/span><\/div>\n<div><span class=\"style-scope yt-formatted-string\" dir=\"auto\" face=\"Roboto, Arial, sans-serif\" style=\"background: rgba(0, 0, 0, 0.05); border: 0px; color: #0f0f0f; font-size: 14px; margin: 0px; padding: 0px; white-space: pre-wrap;\"> <iframe loading=\"lazy\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen=\"\" frameborder=\"0\" height=\"247\" src=\"https:\/\/www.youtube.com\/embed\/LmJQO8umScA?rel=0\" title=\"YouTube video player\" width=\"440\"><\/iframe> <br \/><\/span><\/div>\n","protected":false},"excerpt":{"rendered":"<p>Here is another update on Direct Conversion receiver construction. In Northern Virginia we get very strong signals from the Radio Marti transmitter in Greenville NC. During the morning hours it is just above the 40 meter band at 7335 kHz. In the evening it is a bit higher in frequency at 7435 KHz. (in the &hellip; <a href=\"https:\/\/www.homebrewradio.us\/blog\/2022\/11\/09\/direct-conversion-receiver-simple-2-diode-mixer-defeats-radio-marti-but-diode-ring-is-the-best\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Direct Conversion Receiver &#8212; Simple 2-Diode Mixer Defeats Radio Marti, but Diode Ring is the Best&#8221;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35,34,72,12],"tags":[],"class_list":["post-6120","post","type-post","status-publish","format-standard","hentry","category-direct-conversion","category-mixer-theory","category-short-wave-listening","category-tj-dc-rx"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/6120","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\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=6120"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/6120\/revisions"}],"predecessor-version":[{"id":11345,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/6120\/revisions\/11345"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=6120"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=6120"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=6120"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}