{"id":2650,"date":"2017-10-02T10:04:00","date_gmt":"2017-10-01T23:04:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2017\/10\/02\/trghs-i-can-hear-the-roosters-of-boa-vista\/"},"modified":"2025-07-21T13:40:08","modified_gmt":"2025-07-21T03:40:08","slug":"trghs-i-can-hear-the-roosters-of-boa-vista","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2017\/10\/02\/trghs-i-can-hear-the-roosters-of-boa-vista\/","title":{"rendered":"TRGHS: I Can Hear the Roosters of Boa Vista"},"content":{"rendered":"
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At the instigation of Bob N7SUR I’ve been working on a simple, easy-to-reproduce Direct Conversion receiver for 40 meters. I’m building this for my nephew John Henry, and I’m hoping this will be a circuit that others can use to break into the ELITE corp of successful ham receiver builders. Coincidentally Joh in Freiburg Germany is working on a very similar project — we have been comparing notes. <\/b>

<\/b> At first I used an FET detector described by Miguel PY2OHH. It worked, but at night the AM detection of powerful shortwave broadcast stations drowned out the amateur signals. So Joh and I started to explore detectors that would eliminate this problem. I went with a version of one described in SPRAT by F5LVG ( “The RX-20 Receiver”- see below). Very simple: A transformer to two back-to-back diodes with a 1K pot to balance the signal from the VFO. OM Olivier used a very, very cool transformer: he took two small, molded chokes and simply glued them together! 22uH choke as the primary, 100uH choke as the secondary. I went with one of the toroidal transformers that Farhan left me when he visited in May. <\/b>

<\/b> I’m using a varactor-controlled ceramic resonator VXO (no Si5351 in this one!) and a non-IC AF amp designed for use with ear buds (the world is awash in ear buds). It is a “singly balanced” design with the incoming RF signal being the one “balanced out” in the detector. <\/b>

<\/b> Last night the receiver passed the AM breakthrough test. The SW broadcast monsters were balanced out and kept at bay. <\/b>

<\/b> This morning the receiver passed The Boa Vista Rooster Detection Test. I fired up the receiver and heard an operator speaking Spanish with a Brazilian accent. When I heard the rooster crowing in the background I knew it was Helio PV8AL from Boa Vista Brazil<\/a>. TRGHS — this little receiver is a winner. <\/b>

<\/b> I’ll try to post a schematic soon. <\/b>

<\/b> And hey — look at what wonderful IBEW (International Brotherhood of Electronic Wizards) project this is: Instigation and inspiration from Oregon. Some design ideas from Brazil. A French detector circuit described in a British QRP magazine. A transformer from India. A collaborator in Germany. And finally, the rooster of Boa Vista. <\/b>

<\/b> <\/p>\n

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<\/div>\n
Let’s not forget Wes Hayward W7ZOI for bringing back (in 1968!) the neglected Direct Conversion idea.<\/b><\/div>\n","protected":false},"excerpt":{"rendered":"

At the instigation of Bob N7SUR I’ve been working on a simple, easy-to-reproduce Direct Conversion receiver for 40 meters. I’m building this for my nephew John Henry, and I’m hoping this will be a circuit that others can use to break into the ELITE corp of successful ham receiver builders. Coincidentally Joh in Freiburg Germany … Continue reading “TRGHS: I Can Hear the Roosters of Boa Vista”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":2651,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[217,35,227,95,60,68,17,119],"tags":[],"class_list":["post-2650","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-brazil","category-direct-conversion","category-france","category-germany","category-hayward-wes","category-india","category-sprat","category-uk"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2650","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=2650"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2650\/revisions"}],"predecessor-version":[{"id":2653,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/2650\/revisions\/2653"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/2651"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=2650"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=2650"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=2650"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}