{"id":5638,"date":"2013-10-20T12:07:00","date_gmt":"2013-10-20T01:07:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2013\/10\/20\/bitx-build-update-15-necessary-mic-amp-mod\/"},"modified":"2013-10-20T12:07:00","modified_gmt":"2013-10-20T01:07:00","slug":"bitx-build-update-15-necessary-mic-amp-mod","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2013\/10\/20\/bitx-build-update-15-necessary-mic-amp-mod\/","title":{"rendered":"BITX Build Update #15 &#8212; Necessary Mic Amp Mod"},"content":{"rendered":"<p><strong>I was having trouble with the mic amp on my new Manhattan Discrete BITX 17. I had it wired as per the schematic, but it just wasn&#8217;t working right &#8212; I was getting very little DSB out of the balanced nodulator, but everything worked fine if I 1) unbalanced the bal mod or 2) injected audio (from a sig generator) directly into the audio in port of the balancec modulator. Clearly something was wrong in the mic amp circuit. I noticed the collector voltage seemed quite low.<\/strong><br \/> <strong><\/strong><br \/> <strong>Some quick Googling revealed that others had struggled a bit with this problem also. Nicolae&#8217;s note was especially illuminating and useful: <\/strong><br \/> <a href=\"http:\/\/users.tpg.com.au\/nfieraru\/Electronics\/BitX20_Mic_Preamp.htm\"><strong>http:\/\/users.tpg.com.au\/nfieraru\/Electronics\/BitX20_Mic_Preamp.htm<\/strong><\/a><br \/> <strong><\/strong><br \/> <strong>As Nicolae noted, the 10K value may have worked with lower gain transistors. We must remember that BITX was (very admirably) designed for minimal cost and maximum use of scrounged parts. <\/strong><br \/> <strong><\/strong><br \/> <strong>I swapped the 10K resistor for a 39K and all is right with the world. The band is not yet open here, but I bravely called a European aeronautical mobile station, hoping that he would be my first QSO on this rig. I think he heard me, but no QSO (yet!).<\/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>I was having trouble with the mic amp on my new Manhattan Discrete BITX 17. I had it wired as per the schematic, but it just wasn&#8217;t working right &#8212; I was getting very little DSB out of the balanced nodulator, but everything worked fine if I 1) unbalanced the bal mod or 2) injected &hellip; <a href=\"https:\/\/www.homebrewradio.us\/blog\/2013\/10\/20\/bitx-build-update-15-necessary-mic-amp-mod\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;BITX Build Update #15 &#8212; Necessary Mic Amp Mod&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28],"tags":[],"class_list":["post-5638","post","type-post","status-publish","format-standard","hentry","category-bitx20"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/5638","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=5638"}],"version-history":[{"count":0,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/5638\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=5638"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=5638"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=5638"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}