I pulled a pill bottle out of my junk box, it had a single layer of solid enameled wire wound on it, and it measured 85 microhenrys. So I added the transistor, resistors and the capacitors to get it to oscillate at the low end of the AM BCB, around 540 kHz.<\/p>\n
The schem is the same as the one here<\/a>, but with different values.<\/p>\n The circuit is the standard Colpitts with the tap between the two capacitors connected to the emitter and the hot end of the coil\/capacitor is connected to the base. The coil must have a 0.1 uF DC blocking capacitor to prevent the base bias from shunting to negative. The supply voltage is 9 volts, but it will oscillate at much lower voltages.<\/p>\n I soldered the coil wire to the wrong point, putting the coil across the power supply wires. I put it on the power supply I made from a wall wart, and I was puzzled why the power supply output went to zero. I think the short burned out the fuse inside the wall wart, because after I fixed the coil short, the power supply didn’t put out any voltage. So I have another thing to repair.<\/p>\n The oscillator can be heard strongly when it’s a few feet from the receiver antenna, but I moved it across the room and the signal quickly disappeared into the noise. I when added a few feet of wire to the emitter to make an antenna, the signal was better, I could barely hear it across the room.<\/p>\n I lengthened the short antenna I had connected to the emitter, to extend the range, but I didn’t hear it on the receiver. I think the frequency changed due to the longer antenna.<\/p>\n More experimenting with this soon.<\/p>\n","protected":false},"excerpt":{"rendered":" I pulled a pill bottle out of my junk box, it had a single layer of solid enameled wire wound on it, and it measured 85 microhenrys. So I added the transistor, resistors and the capacitors to get it to oscillate at the low end of the AM BCB, around 540 kHz. The schem is <\/p>\n (Read More…)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[74,78,7,296,261],"tags":[],"class_list":["post-12064","post","type-post","status-publish","format-standard","hentry","category-electronic-components","category-inductors","category-radio-frequency","category-schematics","category-transmitter"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/12064","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=12064"}],"version-history":[{"count":9,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/12064\/revisions"}],"predecessor-version":[{"id":12082,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/12064\/revisions\/12082"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12064"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12064"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12064"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}