{"id":3987,"date":"2014-01-05T13:40:00","date_gmt":"2014-01-05T02:40:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2014\/01\/05\/bitx-20-40-build-update-4-11mhz-ssb-ladder-filter\/"},"modified":"2025-07-21T16:23:30","modified_gmt":"2025-07-21T06:23:30","slug":"bitx-20-40-build-update-4-11mhz-ssb-ladder-filter","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2014\/01\/05\/bitx-20-40-build-update-4-11mhz-ssb-ladder-filter\/","title":{"rendered":"BITX 20\/40 BUILD UPDATE #4: 11MHz SSB Ladder Filter"},"content":{"rendered":"
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As reported yesterday I have the 20 meter receiver portion of my BITX 20\/40 rig up and running. I decided to take a closer look at the crystal filter I built. <\/b><\/div>\n

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Here is my method: <\/b><\/div>\n

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1) Using an Arduino\/DDS sig generator, I put 11 Mhz energy into the base of Q2 (the stage immediately prior to the crystal filter). <\/b><\/div>\n

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2) Using my Rigol 1052E oscilloscope, I measured RMS voltage at the output of Q3\/Q3A (the stage immediately following the filter). <\/b><\/div>\n

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3) I looked at Vrms as I MANUALLY varied the input frequency in 100 Hz increments.<\/b><\/div>\n

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4) I took the results and plugged them into a spreadsheet. I then used the spreadsheet to calculate the db drop from the peak Vrms value (So I wasn’t looking at insertion loss, just the filter shape). <\/b><\/div>\n
I used 20*LOG(Vrms\/276)<\/b><\/div>\n

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5) I ended up with the chart displayed above. <\/b><\/div>\n

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I have a few questions: <\/b><\/div>\n
1) What do you folks think about my methodology for evaluating the filter? <\/b><\/div>\n
2) Where would you guys put the BFO frequency? <\/b><\/div>\n
3) I know the ripple looks ugly, but the receiver sounds great. Should I attempt to get rid of the ripple? <\/b><\/div>\n

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Here is the filter I used (as prescribed by the AADE software): I estimated Q at 10000 and used LM and CM values derived by the G3UUR method, and made no effort to match impedances going into the filter: <\/b><\/div>\n
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Here is what GPLA predicted. I estimated Rin and Rout values. That probably accounts for the difference between the GPLA prediction and what I measured. <\/b><\/div>\n
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Our book: “SolderSmoke — Global Adventures in Wireless Electronics” http:\/\/soldersmoke.com\/book.htm<\/a> Our coffee mugs, T-Shirts, bumper stickers: http:\/\/www.cafepress.com\/SolderSmoke<\/a> Our Book Store: http:\/\/astore.amazon.com\/contracross-20<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

As reported yesterday I have the 20 meter receiver portion of my BITX 20\/40 rig up and running. I decided to take a closer look at the crystal filter I built. Here is my method: 1) Using an Arduino\/DDS sig generator, I put 11 Mhz energy into the base of Q2 (the stage immediately prior … Continue reading “BITX 20\/40 BUILD UPDATE #4: 11MHz SSB Ladder Filter”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":3988,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,16,71],"tags":[],"class_list":["post-3987","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bitx20","category-filters","category-test-gear"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/3987","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=3987"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/3987\/revisions"}],"predecessor-version":[{"id":3991,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/3987\/revisions\/3991"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/3988"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=3987"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=3987"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=3987"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}