{"id":329,"date":"2022-02-25T11:03:09","date_gmt":"2022-02-25T11:03:09","guid":{"rendered":"https:\/\/fletch.scot\/wp\/?p=329"},"modified":"2022-06-13T13:07:40","modified_gmt":"2022-06-13T12:07:40","slug":"switchable-lpf-response","status":"publish","type":"post","link":"https:\/\/fletch.scot\/wp\/?p=329","title":{"rendered":"Switchable LPF Response"},"content":{"rendered":"<p>The <a href=\"https:\/\/www.ebay.co.uk\/itm\/175022524110?hash=item28c027c6ce:g:jFEAAOSw6z1gm~XT\">switchable LPF<\/a>\u00a0for my\u00a0<a href=\"https:\/\/fletch.scot\/wp\/?p=319\">WSPR Transmitter<\/a>\u00a0finally arrived and I\u2019ve made some response graphs to test how it performs.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"IMG_0222.jpeg\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/IMG_0222.jpeg\" alt=\"Test setup for Switchable LPF\" width=\"599\" height=\"266\" border=\"0\" \/><\/p>\n<p>The obvious bit of test kit to check out the LPFs is my nanoVNA. I suggest you buy a nanoVNA from a reputable dealer as there are plenty of clones which don\u2019t work as well as the original.<\/p>\n<p>The test setup is above. The 27 V in the drawing can go as low as 13.8 V, but will not work at any lower voltage.\u00a0<\/p>\n<p>As I\u2019ve mentioned before I find the small screen on the nanoVNA difficult to control with my clumsy hands. So I wrote another simple MATLAB script <a href=\"https:\/\/fletch.scot\/code\/nanoVNA\/ajfLogMagS21.m\">ajfLogMagS21<\/a> to drive the nanoVNA to get the response charts. The calibration done as before using my <a href=\"https:\/\/fletch.scot\/code\/nanoVNA\/ajfCalibrate.m\">ajfCalibrate<\/a> MATLAB script. The LPFs will attenuate the harmonics by 25 dB which will be enough for my feeble WSPR output.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 1.9 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-1.9-MHz-Response.png\" alt=\"RV3YF LPF 1 9 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 3.5 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-3.5-MHz-Response.png\" alt=\"RV3YF LPF 3 5 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 7-10 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-7-10-MHz-Response.png\" alt=\"RV3YF LPF 7 10 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 14 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-14-MHz-Response.png\" alt=\"RV3YF LPF 14 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 18 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-18-MHz-Response.png\" alt=\"RV3YF LPF 18 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p>\u00a0<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 21 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-21-MHz-Response.png\" alt=\"RV3YF LPF 21 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" title=\"RV3YF LPF 24-28 MHz Response.png\" src=\"https:\/\/fletch.scot\/wp\/wp-content\/uploads\/2022\/02\/RV3YF-LPF-24-28-MHz-Response.png\" alt=\"RV3YF LPF 24 28 MHz Response\" width=\"600\" height=\"450\" border=\"0\" \/><\/p>\n<p>The next step is work out how to drive the switching of the bands. First thoughts are to send commands via I2C and have something convert that to a 13.8-27 V signal on the appropriate pin. I2C is attractive as I already have an I2C bus in the <a href=\"https:\/\/fletch.scot\/wp\/?p=319\">WSPR Transmitter<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The switchable LPF\u00a0for my\u00a0WSPR Transmitter\u00a0finally arrived and I\u2019ve made some response graphs to test how it performs. The obvious bit of test kit to check out the LPFs is my nanoVNA. I suggest you buy a nanoVNA from a reputable dealer as there are plenty of clones which don\u2019t work as well as the original. &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/fletch.scot\/wp\/?p=329\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Switchable LPF Response&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[6,56],"class_list":["post-329","post","type-post","status-publish","format-standard","hentry","tag-aerial","tag-wspr"],"_links":{"self":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/329","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=329"}],"version-history":[{"count":5,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/329\/revisions"}],"predecessor-version":[{"id":342,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=\/wp\/v2\/posts\/329\/revisions\/342"}],"wp:attachment":[{"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=329"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=329"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fletch.scot\/wp\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=329"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}