{"id":7999,"date":"2023-09-08T21:08:00","date_gmt":"2023-09-08T11:08:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2023\/09\/08\/why-building-for-10-meters-is-harder-than-building-for-lower-frequencies\/"},"modified":"2025-07-22T18:02:04","modified_gmt":"2025-07-22T08:02:04","slug":"why-building-for-10-meters-is-harder-than-building-for-lower-frequencies","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2023\/09\/08\/why-building-for-10-meters-is-harder-than-building-for-lower-frequencies\/","title":{"rendered":"Why Building for 10 Meters is Harder than Building for Lower Frequencies"},"content":{"rendered":"

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<\/b>Recently my trusty CCI EB63A .1kW amplifier has been in rebellion. On 10 meters, it now often insists on being an oscillator. It calms down nicely on 20 meters. But on 10, it has been a rebellious beast. <\/b><\/p>\n

Why is this? Why would an amplifier that is well behaved and stable on 20 meters behave so badly on 10 meters? <\/b><\/p>\n

I used LTSpice to explore the problem. <\/b><\/p>\n

I looked at two ordinary wires. I gave them each a value of .003 uH. Very low. Then I joined them together in a transformer. I put a 1 volt signal into the primary and looked (in LTSpice) at how much of a signal appeared in the secondary. First, the result on 14 MHz. About 250 mV appears on the secondary. <\/b><\/p>\n<\/p>\n

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Now consider what happens at 28 MHz. Nothing else in the circuit changes. Just the frequency.<\/b><\/div>\n
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Here we get about 450 mV. A lot more. <\/b><\/div>\n

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Realize that my little EB63A amp has lots of wires in it, most of which are ready to serve as primary or secondaries in circuits like this. Increasing the frequency makes it more likely that a ginal will jump to someplace that it is not supposed to be. Output will couple to input and the Barkhausen criteria will be met. The amplifier will become an oscillator. <\/b><\/div>\n

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Of course, something similar happens with capacitive coupling. Same story: the higher the frequency, the harder it is to keep the amplifier stable. <\/b><\/div>\n

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Don’t worry: Improved shielding is saving the day. The amplifier is now stable on 10. More about this in the next podcast… <\/b><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Recently my trusty CCI EB63A .1kW amplifier has been in rebellion. On 10 meters, it now often insists on being an oscillator. It calms down nicely on 20 meters. But on 10, it has been a rebellious beast. Why is this? Why would an amplifier that is well behaved and stable on 20 meters behave … Continue reading “Why Building for 10 Meters is Harder than Building for Lower Frequencies”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":8000,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[124,84],"tags":[],"class_list":["post-7999","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-10-meters","category-amplifier-theory"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7999","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\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=7999"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7999\/revisions"}],"predecessor-version":[{"id":8003,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7999\/revisions\/8003"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/8000"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=7999"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=7999"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=7999"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}