{"id":4417,"date":"2024-03-26T11:10:00","date_gmt":"2024-03-26T00:10:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2024\/03\/26\/how-to-feel-bad-about-carrier-suppression-and-how-to-get-over-it\/"},"modified":"2025-07-22T18:01:41","modified_gmt":"2025-07-22T08:01:41","slug":"how-to-feel-bad-about-carrier-suppression-and-how-to-get-over-it","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2024\/03\/26\/how-to-feel-bad-about-carrier-suppression-and-how-to-get-over-it\/","title":{"rendered":"How to Feel Bad about Carrier Suppression (and How to Get Over It)"},"content":{"rendered":"<p><iframe loading=\"lazy\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" allowfullscreen=\"\" frameborder=\"0\" height=\"247\" referrerpolicy=\"strict-origin-when-cross-origin\" src=\"https:\/\/www.youtube.com\/embed\/q66YkSwyh9w?si=lUFNLTU21IysND4S?rel=10\" title=\"YouTube video player?rel=0\" width=\"440\"><\/iframe><\/p>\n<div><\/div>\n<div><b>Version 2 of the 15-10 rig continues to give me trouble. But I guess it is &#8220;good trouble&#8221; because I am learning from it. <\/b><\/div>\n<div><b><br \/><\/b><\/div>\n<div><b>You see, after you build an SSB rig, one of the critical alignment steps is the placement of the carrier oscillator\/BFO frequency in relation to the filter passband. (The IMSAI Guy has a good video on this &#8212; see above.) You want to place this oscillator somewhere on the downward skirt of the passband curve. This will add to the carrier suppression already done by your balanced modulator. There will always be some carrier remaining from the balanced modulator &#8212; putting the oscillator frequency on the downward skirt of the filter passband adds to the suppression the carrier remnant. <\/b><\/div>\n<div><b><br \/><\/b><\/div>\n<div><b>But you can&#8217;t overdo it. If you place that carrier oscillator frequency too far down on the skirt, you will start to cutoff the low audio frequencies in your transmit and received signals. You will notice that your once beautiful sounding receiver suddenly sounds tinny and high pitched. Yuck. <\/b><\/div>\n<div><b><br \/><\/b><\/div>\n<div><b>So you go back to the books and the websites. You look at the passband promissed by the Dishal software you used to design the filter. See below: <\/b><\/p>\n<div><\/div>\n<div>\n<div class=\"separator\" style=\"clear: both; text-align: center;\"><a href=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2024\/03\/image_1753081734.png\" style=\"margin-left: 1em; margin-right: 1em;\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" data-original-height=\"600\" data-original-width=\"740\" height=\"240\" src=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2024\/03\/image_1753081734.png\" width=\"296\" \/><\/a><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: center;\"><span style=\"font-size: x-small;\">Click on the image for a better view<\/span><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b>Surely with a passband as nice as that one, you will be able to find the sweet spot where the carrier is suppressed and your audio remains pristine. <\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b><br \/><\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b>But I couldn&#8217;t do this with the 15-10 rig. I was forced to compromise: I had to accept less than optimal carrier suppression for less than optimal low frequency passband coverage. And here is why:<\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\">\n<div class=\"separator\" style=\"clear: both; font-weight: bold; text-align: center;\"><a href=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2024\/03\/image_1753081737.png\" style=\"margin-left: 1em; margin-right: 1em;\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" data-original-height=\"768\" data-original-width=\"949\" height=\"240\" src=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2024\/03\/image_1753081737.png\" width=\"297\" \/><\/a><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: center;\"><span style=\"font-size: x-small;\">Click on the image for a better view<\/span><\/div>\n<\/div>\n<div class=\"separator\" style=\"clear: both; text-align: center;\"><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b>The curve above is a much more realistic picture of what my filter passband actually looks like (see NanoVNA picture below). The curve above is from the AADE software. I found out that the Dishal software DOES NOT factor in important things like Q or ESR. Dishal treats all crystals as &#8220;loss-less radiators.&#8221; So when you get up to 25 MHz where Q is important, AADE and other programs will show you that your passband has become curved. And you can see how this curvature makes it difficult to get the kind of carrier suppression and audio response we want. <\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b><br \/><\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b><\/p>\n<div class=\"separator\" style=\"clear: both; text-align: center;\"><a href=\"https:\/\/blogger.googleusercontent.com\/img\/a\/AVvXsEiFk8Cq7nyHxdciEHN23tG8qYvic1u29mBFbSRc3-XYOfUpSgiy6rNiNPbQcMdrTOm3kZLKR6qfUqmzieDWsbgtROkcOlPt18KqHiv8NV-nd2F42scKSwDAp0UIgfd9hR3DOneiHDKPW4xab4rJOcjsKAQCdjRq-8LgUwCI0rrXgBYTkqzMbI25YYwv_Yg\" style=\"margin-left: 1em; margin-right: 1em;\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" data-original-height=\"4032\" data-original-width=\"3024\" height=\"400\" src=\"https:\/\/www.homebrewradio.us\/blog\/wp-content\/uploads\/2024\/03\/image_1753081739.jpg\" width=\"300\" \/><\/a><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: center;\">What my filter looked like in a Nano VNA<\/div>\n<div class=\"separator\" style=\"clear: both; text-align: center;\"><span style=\"font-size: x-small;\">Click for a better view<\/span><\/div>\n<p><\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b><br \/><\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b>Look, the rigs work OK. The receivers sound good to me. The carrier is so far down that no one can hear it. I have to remind myself that we are using &#8216;SSB-SC&#8221; &#8212; suppressed carrier, not eliminated carrier. I&#8217;ve worked a lot of DX with these rigs. But still, I would like to improve the situation. It kind of bothers me. Homebrewers will understand. <\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b><br \/><\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b>I have been experimenting with different balanced modulators. I started with the simple two diode, single transformer, singly balanced design from Farhan&#8217;s BITX20. It works fine. But I think I get a bit better suppresson from a doubly balanced diode ring. I may try an NE602 Gilbert Cell. I may also try to build a higher Q 25 MHz filter using low-ESR surface mount crystals from Mouser. Stay tuned. <\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b><br \/><\/b><\/div>\n<div class=\"separator\" style=\"clear: both; text-align: left;\"><b>Thanks to W7ZOI, VU2ESE, WN2A, KA4KXX, KK4DAS, N6QW, W2AEW, and G3UUR for all the good advice and encouragement. Please put any additional ideas in the comments below. <\/b><\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Version 2 of the 15-10 rig continues to give me trouble. But I guess it is &#8220;good trouble&#8221; because I am learning from it. You see, after you build an SSB rig, one of the critical alignment steps is the placement of the carrier oscillator\/BFO frequency in relation to the filter passband. (The IMSAI Guy &hellip; <a href=\"https:\/\/www.homebrewradio.us\/blog\/2024\/03\/26\/how-to-feel-bad-about-carrier-suppression-and-how-to-get-over-it\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;How to Feel Bad about Carrier Suppression (and How to Get Over It)&#8221;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":4418,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16,23],"tags":[],"class_list":["post-4417","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-filters","category-ssb"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/4417","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=4417"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/4417\/revisions"}],"predecessor-version":[{"id":4421,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/4417\/revisions\/4421"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/4418"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=4417"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=4417"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=4417"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}