{"id":611,"date":"2021-10-25T10:49:00","date_gmt":"2021-10-24T23:49:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2021\/10\/25\/putting-a-ceramic-filter-in-the-mate-for-the-mighty-midget-receiver\/"},"modified":"2025-07-22T18:04:31","modified_gmt":"2025-07-22T08:04:31","slug":"putting-a-ceramic-filter-in-the-mate-for-the-mighty-midget-receiver","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2021\/10\/25\/putting-a-ceramic-filter-in-the-mate-for-the-mighty-midget-receiver\/","title":{"rendered":"Putting a Ceramic Filter in the “Mate for the Mighty Midget” Receiver"},"content":{"rendered":"<\/p>\n
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It is really simple. I had one of the +\/- 3kHz (6 kHz wide) 455HT filters on hand. The spec sheets call for 2000 ohms at both ends, but looking at the schematic it appeared that I already had high impedance on both sides of the filter. I put a .001 uF cap on the input side to keep the DC voltage off the filter (see above and below). This capacitor allows us to avoid the dreaded problem of electro-migration that is so nicely described by SV8YM here: <\/b><\/div>\n

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http:\/\/sv8ym.blogspot.com\/2010\/07\/mysterious-case-of-withering-filters.html<\/a>. <\/b><\/div>\n

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Tasos also provides a good description of the innards of those little black boxes that contain ceramic filters. <\/b><\/div>\n

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Once you get the filter in your receiver, you have to carefully place the BFO signal in relation to the filter passband. I have trouble properly sweeping 455 kHz filters — my HP8640B will not go that low. Nor will my Antuino (I need to modify the code — someone help me please). I know the NanoVNA will do the job, but I just couldn’t seem to get it to work. So I went “old-school” and manually swept the filter using my FeelTech sig gen and my Rigol scope. This gave me a rough idea of where the passband was. I put the BFO on the low end of the filter passband, at 451 kHz.<\/b><\/div>\n

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With this filter the MMM RX has become a real asset. The 6 kHz bandwidth allows for nice reception of both SSB signals and AM sigs. I may try to use one of the +\/- 2 kHz filters (4 KHz wide), but so far I have not been able to find a source for this part. <\/b><\/div>\n

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It is really simple. I had one of the +\/- 3kHz (6 kHz wide) 455HT filters on hand. The spec sheets call for 2000 ohms at both ends, but looking at the schematic it appeared that I already had high impedance on both sides of the filter. I put a .001 uF cap on the … Continue reading “Putting a Ceramic Filter in the “Mate for the Mighty Midget” Receiver”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":612,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[109,93,16,201,200,191],"tags":[],"class_list":["post-611","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-antuino","category-ceramic-resonators","category-filters","category-greece","category-mate-for-the-mighty-midget","category-nanovna"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/611","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=611"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/611\/revisions"}],"predecessor-version":[{"id":614,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/611\/revisions\/614"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/612"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=611"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=611"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=611"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}