{"id":16770,"date":"2026-03-31T07:30:54","date_gmt":"2026-03-31T02:00:54","guid":{"rendered":"https:\/\/johnsonfrancis.org\/techworld\/?p=16770"},"modified":"2026-03-31T08:42:27","modified_gmt":"2026-03-31T03:12:27","slug":"having-a-close-look-at-the-integrated-circuits-in-lmr-sdr-1-1","status":"publish","type":"post","link":"https:\/\/johnsonfrancis.org\/techworld\/having-a-close-look-at-the-integrated-circuits-in-lmr-sdr-1-1\/","title":{"rendered":"Having a close look at the integrated circuits in LMR SDR 1.1"},"content":{"rendered":"<p><iframe loading=\"lazy\" width=\"560\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/_HXkYpAf4vY?si=bPncDZ08v9o7RSFy\" title=\"YouTube video player\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/p>\n\n\n<p class=\"wp-block-paragraph\">I have bought five integrated circuits along with the LMR SDR 1.1 PCB. Thought of having a look at them and learning their main functions. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>HD74LS145P<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It is a is a BCD-to-Decimal Decoder\/Driver integrated circuit (IC). It is designed to take a 4-bit Binary Coded Decimal (BCD) input and activate one of ten decimal outputs. This IC comes in a 16-pin Dual In-line Package (DIP). The 16 pins are arranged as follows (top view, with the notch on the left):<br>Inputs: Pins 12, 13, 14, 15 (BCD inputs A, B, C, D). Outputs: Pins 1\u20137 and 9\u201311 (Decimal outputs 0\u20139).<br>Power: Pin 16 is (+5V) and Pin 8 is GND.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Had a look at HD74LS145 linked to Arduino Nano in LMR SDR 1.1 Schematic. It is providing outputs for 10 bands from pins 1 to 10 (160m, 80m, 40m, 20m, 17m, 15m, 12m and 10m). That covers the usual HF bands including the WARC bands. It decodes 4-bit Binary Coded Decimal (BCD) signals coming from the microcontroller Arduino Nano into ten separate decimal outputs for each of the amateur radio bands, functioning as a band selection control. Because it features high-performance, open-collector n-p-n output transistors capable of sinking up to 80mA, it is used to directly drive the relays for the onboard Band Pass Filters (BPF) and Low Pass Filters (LPF).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SN74AC74N<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The SN74AC74N is a dual positive-edge-triggered D-type flip-flop in a 14-pin PDIP (Plastic Dual-In-line Package). It contains two independent flip-flops, each with its own data (D), clock (CLK), preset (PRE), and clear (CLR) inputs, along with complementary outputs. In LMR SDR 1.1 it serves as a quadrature clock generator.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its primary function is to take a high-frequency clock signal from the oscillator Si5351 and divide it down to produce two square wave signals that are exactly\u00a0<strong>90 degrees out of phase<\/strong>\u00a0with each other. These &#8220;I&#8221; (In-phase) and &#8220;Q&#8221; (Quadrature) clock signals are then used to drive a\u00a0<strong>Mixer<\/strong>\u00a0for frequency down-conversion or up-conversion. There are three more ICs and the Si5351 mounted as a surface mount device on reverse side of the board. Keep tuned for updates!<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I have bought five integrated circuits along with the LMR SDR 1.1 PCB. Thought of having a look at them and learning their main functions. HD74LS145P It is a is a BCD-to-Decimal Decoder\/Driver integrated circuit (IC). It is designed to take a 4-bit Binary Coded Decimal (BCD) input and activate one of ten decimal outputs. [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-16770","post","type-post","status-publish","format-standard","hentry","category-amateur-radio-ham-radio"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Having a close look at the integrated circuits in LMR SDR 1.1 - Johnson&#039;s Techworld<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/johnsonfrancis.org\/techworld\/having-a-close-look-at-the-integrated-circuits-in-lmr-sdr-1-1\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Having a close look at the integrated circuits in LMR SDR 1.1 - Johnson&#039;s Techworld\" \/>\n<meta property=\"og:description\" content=\"I have bought five integrated circuits along with the LMR SDR 1.1 PCB. Thought of having a look at them and learning their main functions. HD74LS145P It is a is a BCD-to-Decimal Decoder\/Driver integrated circuit (IC). It is designed to take a 4-bit Binary Coded Decimal (BCD) input and activate one of ten decimal outputs. 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Thought of having a look at them and learning their main functions. HD74LS145P It is a is a BCD-to-Decimal Decoder\/Driver integrated circuit (IC). It is designed to take a 4-bit Binary Coded Decimal (BCD) input and activate one of ten decimal outputs. 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