{"id":2563,"date":"2015-08-07T22:39:00","date_gmt":"2015-08-07T12:39:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2015\/08\/07\/amplifier-woes-instability-at-low-drive-levels-video\/"},"modified":"2015-08-07T22:39:00","modified_gmt":"2015-08-07T12:39:00","slug":"amplifier-woes-instability-at-low-drive-levels-video","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2015\/08\/07\/amplifier-woes-instability-at-low-drive-levels-video\/","title":{"rendered":"Amplifier Woes!  Instability at Low Drive Levels!  (Video)"},"content":{"rendered":"<p><iframe loading=\"lazy\" allowfullscreen=\"\" frameborder=\"0\" height=\"330\" src=\"https:\/\/www.youtube.com\/embed\/zTSmGM7pOOo?rel=0\" width=\"440\"><\/iframe><\/p>\n<p> <strong>I have to keep reminding myself: This is not &#8220;plug and play.&#8221; These are not appliances. <\/strong><br \/> <strong><\/strong><br \/> <strong>After I got my 40 meter problems squared away, I was doing some testing on my beloved 17 meter BITX. I noticed something weird: With the CCI EB63A amp feeding my 17 meter Moxon antenna, as I raised the output of the BITX17 driver, at one point (at about half the max input power) the SWR would suddenly spike. Then, as I raised the drive level above that point, the SWR would go back to normal. <\/strong><br \/> <strong><\/strong><br \/> <strong>I looked at it on the &#8216;scope. I can see the signal go very ugly at the mid-level drive point. In the FFT display, I can see that there is a strong signal at around 435 kHz. The 18 MHz signal seems to be riding along on top of it. Take a look at the video above. <\/strong><br \/> <strong><\/strong><br \/> <strong>Additional clues: <\/strong><br \/> <strong><\/strong><br \/> <strong>I see no signs of the 435 kHz signal at the output of the BITX 17. It seems quite clean. <\/strong><br \/> <strong><\/strong><br \/> <strong>This problem disappears if I replace the Moxon with a dummy load. <\/strong><br \/> <strong><\/strong><br \/> <strong>This problem does not show up if I feed the EB63A with my almost identical BITX20. And I use the same LP filter on both 20 and 17 in the CCI amp. <\/strong><br \/> <strong><\/strong><br \/> <strong>Any suggestions? Has anyone had this kind of problem? <\/strong><br \/> <strong><\/strong><br \/> <strong>Allison and Pete have been helping me with this. Thanks to both of them. <\/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 have to keep reminding myself: This is not &#8220;plug and play.&#8221; These are not appliances. After I got my 40 meter problems squared away, I was doing some testing on my beloved 17 meter BITX. I noticed something weird: With the CCI EB63A amp feeding my 17 meter Moxon antenna, as I raised the &hellip; <a href=\"https:\/\/www.homebrewradio.us\/blog\/2015\/08\/07\/amplifier-woes-instability-at-low-drive-levels-video\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Amplifier Woes!  Instability at Low Drive Levels!  (Video)&#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":[28,71,25],"tags":[],"class_list":["post-2563","post","type-post","status-publish","format-standard","hentry","category-bitx20","category-test-gear","category-troubleshooting"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2563","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=2563"}],"version-history":[{"count":0,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2563\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=2563"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=2563"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=2563"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}