Also posted to FB group Building Transistor Radios<\/p>\n\n\n\n
Watson\u2019s 9 picofarad homemade \u201cgimmick\u201d capacitor<\/p>\n\n\n\n
This homemade capacitor can be used for circuits were the capacitance\n is not critical, such as a wireless microphone for the FM broadcast \nband. The wire can be obtained from the cable used to connect telephone \noutlets. Solid (not stranded) plastic insulated hookup wire can also be \nused.<\/p>\n\n\n\n
I used about 300 mm or 1 foot of 24 AWG or 0.5mm solid (single conductor, not stranded) plastic insulated wire.<\/p>\n\n\n\n
I cut it into 6 pieces, each 50 mm or 2 inches long. I stripped the insulation 9 mm or 3\/8 inch off one end of each of them.<\/p>\n\n\n\n
I took 3 of the pieces and twisted the bare wires together and soldered them. I did the same for the other 3 pieces.<\/p>\n\n\n\n
I took one wire from each 3 wire piece and twisted them together \ntightly using my long nose pliers. I made sure the insulation was not \ndamaged. I did the same for each of the remaining wires. I then had 3 \ntwisted pairs, and two bare leads to connect to.<\/p>\n\n\n\n
I checked to make sure there were no wires touching on the insulated \nends. Then I twisted the 3 twisted pairs into a tight bundle. I measured\n the capacitance with an LC meter and I got 9 picofarads.<\/p>\n\n\n\n
If the capacitance needs to be reduced I can use only 4 wires or 2 \ntwisted pairs. Or I can make them shorter to begin with, or cut them \nshorter afterwards. I can also untwist the wires to adjust the \ncapacitance and then twist them back together.<\/p>\n\n\n\n
As I said, the pF value is not stable because it depends on how much \ntwists, and how much give there is in the plastic after you build it. \nIf you put it in parallel with a variable cap, then you can compensate \nfor changes over time.<\/p>\n","protected":false},"excerpt":{"rendered":"
Also posted to FB group Building Transistor Radios Watson\u2019s 9 picofarad homemade \u201cgimmick\u201d capacitor This homemade capacitor can be used for circuits were the capacitance is not critical, such as a wireless microphone for the FM broadcast band. The wire can be obtained from the cable used to connect telephone outlets. Solid (not stranded) plastic <\/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":[1],"tags":[],"class_list":["post-13139","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/13139","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=13139"}],"version-history":[{"count":1,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/13139\/revisions"}],"predecessor-version":[{"id":13140,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/13139\/revisions\/13140"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13139"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13139"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13139"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}