{"id":41366,"date":"2019-12-29T08:43:19","date_gmt":"2019-12-29T12:43:19","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=41366"},"modified":"2019-12-29T08:43:19","modified_gmt":"2019-12-29T12:43:19","slug":"understanding-decibels","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2019\/12\/understanding-decibels\/","title":{"rendered":"Understanding decibels"},"content":{"rendered":"<p><a href=\"https:\/\/swling.com\/blog\/wp-content\/uploads\/2017\/12\/CR-1a-Dial-6150-kHz-e1514588791282.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-large wp-image-29861\" src=\"https:\/\/swling.com\/blog\/wp-content\/uploads\/2017\/12\/CR-1a-Dial-6150-kHz-1024x587.jpg\" alt=\"\" width=\"625\" height=\"358\" \/><\/a><\/p>\n<p>Many thanks to <em>SWLing Post<\/em> contributor, Marty, who shares the following article <a href=\"https:\/\/www.nutsvolts.com\/magazine\/article\/January2017_HamsWirelessWorkbench_Ham-Metrics-and-Decibels\" target=\"_blank\" rel=\"noopener noreferrer\">from Nuts and Volts magazine<\/a>&#8211;a primer on decibels:<\/p>\n<blockquote><p>The \u201cdee-bee\u201d is everywhere in ham radio, and is used for characterizing everything from antenna performance to nano-sized signals. Learn the decibel (abbreviated as lower-case \u2018d\u2019 followed by an upper-case \u2018B\u2019 or \u2018dB\u2019) and you and your signal will go a long way!<\/p>\n<p>From the ARRL Ham Radio License Manual\u2019s online math tutorials for beginning hams (<a href=\"http:\/\/arrl.org\/chpt-2-radio-signal-fundamentals\" target=\"_blank\" rel=\"noopener noreferrer\">arrl.org\/chpt-2-radio-signal-fundamentals<\/a>), we introduce the decibel. \u201cYou have probably recognized deci as the metric prefix that means one-tenth. The unit we are really talking about here is the bel (a ratio of sound levels named for Alexander Graham Bell), so a decibel is just 1\/10th of a bel. We use a decibel instead of a whole bel because the bel represents a rather large change in levels. The dB is a just-perceptible change and more useful as a unit of measurement.\u201d As used in wireless, the decibel is the ratio of two power levels:<\/p>\n<p>dB = 10 log10 (P2\/P1)<\/p>\n<p>Note that the dB has no units because it is a ratio. The dB is just a number that describes how much bigger or smaller one quantity is compared to the other. Both quantities themselves must have the same base units, though \u2014 watts, for example. If P2 is larger than P1, the dB value is positive, such as for amplifier gain. If P2 is less, the value is negative and represents attenuation or loss. (Somewhat confusingly, it\u2019s common to specify an amount of attenuation as a positive value of dB. For example, \u201cThis filter attenuates the signal by 20 dB.\u201d)<\/p><\/blockquote>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.nutsvolts.com\/magazine\/article\/January2017_HamsWirelessWorkbench_Ham-Metrics-and-Decibels\" target=\"_blank\" rel=\"noopener noreferrer\">Click here to read the full article at Nuts and Volts.<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Many thanks to SWLing Post contributor, Marty, who shares the following article from Nuts and Volts magazine&#8211;a primer on decibels: The \u201cdee-bee\u201d is everywhere in ham radio, and is used for characterizing everything from antenna performance to nano-sized signals. Learn the decibel (abbreviated as lower-case \u2018d\u2019 followed by an upper-case \u2018B\u2019 or \u2018dB\u2019) and you [&hellip;]<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[545,3,43],"tags":[8227,8226],"class_list":["post-41366","post","type-post","status-publish","format-standard","hentry","category-ham-radio","category-news","category-shortwave-radio","tag-decibels","tag-nuts-and-volts"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pn3uc-aLc","jetpack-related-posts":[{"id":41769,"url":"https:\/\/swling.com\/blog\/2020\/01\/radio-waves-new-bbc-ham-russian-propaganda-rotators-usb-continuity-and-a-moment-of-silence\/","url_meta":{"origin":41366,"position":0},"title":"Radio Waves: New BBC Ham, Russian Propaganda, Rotators, USB Continuity, and a Moment of Silence","author":"Thomas","date":"January 28, 2020","format":false,"excerpt":"Radio Waves:\u00a0 Stories Making Waves in the World of Radio\u00a0 Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest\u00a0SWLing Post\u00a0readers.\u00a0 To that end:\u00a0Welcome to the\u00a0SWLing Post\u2019sRadio Waves, a collection\u2026","rel":"","context":"In &quot;Ham Radio&quot;","block_context":{"text":"Ham Radio","link":"https:\/\/swling.com\/blog\/category\/ham-radio\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2019\/10\/Dial-1024x768.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2019\/10\/Dial-1024x768.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2019\/10\/Dial-1024x768.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":63994,"url":"https:\/\/swling.com\/blog\/2025\/09\/nuts-and-volts-fm-radio-arrives-in-u-s-cars-in-1958\/","url_meta":{"origin":41366,"position":1},"title":"Nuts and Volts: FM Radio Arrives in U.S. Cars in 1958","author":"Thomas","date":"September 21, 2025","format":false,"excerpt":"Many thanks to SWLing Post contributor Dennis Dura for sharing this fascinating Nuts & Volts article exploring the history of FM radio in American automobiles. While AM dominated dashboards for decades, FM began to make its way into U.S. cars in 1958, slowly changing how drivers listened to music and\u2026","rel":"","context":"In &quot;FM&quot;","block_context":{"text":"FM","link":"https:\/\/swling.com\/blog\/category\/fm\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/09\/Analog-Car-Radio-1.jpeg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/09\/Analog-Car-Radio-1.jpeg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/09\/Analog-Car-Radio-1.jpeg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/09\/Analog-Car-Radio-1.jpeg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2025\/09\/Analog-Car-Radio-1.jpeg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":41377,"url":"https:\/\/swling.com\/blog\/2019\/12\/alan-takes-a-deeper-dive-into-decibels\/","url_meta":{"origin":41366,"position":2},"title":"Alan takes a deeper dive into decibels","author":"Thomas","date":"December 31, 2019","format":false,"excerpt":"Many thanks to SWLing Post contributor, Alan Fahrner, who writes: One of your articles below inspired me to write this: https:\/\/math.promo\/2019\/12\/shortwave-decibels\/ This past August I went back for a second bachelors, this time in mathematics. So, I love when real life can be used as an example of answering the\u2026","rel":"","context":"In &quot;News&quot;","block_context":{"text":"News","link":"https:\/\/swling.com\/blog\/category\/news\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/03\/Kenwood-R-2000-Dial.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/03\/Kenwood-R-2000-Dial.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/03\/Kenwood-R-2000-Dial.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/03\/Kenwood-R-2000-Dial.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":43601,"url":"https:\/\/swling.com\/blog\/2020\/05\/radio-technology-magazines-both-online-and-in-print\/","url_meta":{"origin":41366,"position":3},"title":"Radio technology magazines both online and in print","author":"Thomas","date":"May 29, 2020","format":false,"excerpt":"Many thanks to SWLing Post contributor, Mangosman, who writes: There used to be magazines like Radio Electronics (USA), Practical Wireless (UK), Radio Television and Hobbies (Australia) and other magazines on electronics were sold in shops and on subscription for money which paid their writers. The internet has killed most of\u2026","rel":"","context":"In &quot;Ham Radio&quot;","block_context":{"text":"Ham Radio","link":"https:\/\/swling.com\/blog\/category\/ham-radio\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2020\/05\/Practical-Electronics-e1590751899826.jpeg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":52659,"url":"https:\/\/swling.com\/blog\/2022\/05\/radio-waves-drm-part-of-bbc-story-antennas-and-smith-charts-shortwave-hot-debate-carrington-event-and-deep-freeze\/","url_meta":{"origin":41366,"position":4},"title":"Radio Waves: DRM Part of BBC Story, Antennas and Smith Charts, Shortwave &#8220;Hot Debate,&#8221; Carrington Event, and &#8220;Deep Freeze&#8221;","author":"Thomas","date":"May 6, 2022","format":false,"excerpt":"Radio Waves:\u00a0 Stories Making Waves in the World of Radio Welcome to the\u00a0SWLing Post\u2019s Radio Waves, a collection of links to interesting stories making waves in the world of radio.\u00a0Enjoy! DRM Is Part of the BBC World Service Story (Radio World) The iconic broadcaster has been supportive of the standard\u2026","rel":"","context":"In &quot;Antennas&quot;","block_context":{"text":"Antennas","link":"https:\/\/swling.com\/blog\/category\/antennas\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/07\/JRC-NRD-545-Dial.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/07\/JRC-NRD-545-Dial.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/07\/JRC-NRD-545-Dial.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/07\/JRC-NRD-545-Dial.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2017\/07\/JRC-NRD-545-Dial.jpg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":21888,"url":"https:\/\/swling.com\/blog\/2016\/10\/bitx40-a-fully-assembled-45-ssb-qrp-transceiver\/","url_meta":{"origin":41366,"position":5},"title":"BITX40: A Fully Assembled $45 SSB QRP transceiver","author":"Thomas","date":"October 23, 2016","format":false,"excerpt":"Many thanks to Pete (WB9FLW) who writes: Don't know if you have seen this or not. VU2ESE of BITX20 Fame has just introduced the BITX40. This is a fully assembled and tested SSB Transceiver for $45 including shipping from India! http:\/\/www.hfsigs.com\/ Wow! I may have to purchase one of these\u2026","rel":"","context":"In &quot;Ham Radio&quot;","block_context":{"text":"Ham Radio","link":"https:\/\/swling.com\/blog\/category\/ham-radio\/"},"img":{"alt_text":"bitx40v3_main","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/bitx40v3_main-1.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/bitx40v3_main-1.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/bitx40v3_main-1.jpg?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2016\/10\/bitx40v3_main-1.jpg?resize=700%2C400 2x"},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts\/41366","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/comments?post=41366"}],"version-history":[{"count":0,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts\/41366\/revisions"}],"wp:attachment":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/media?parent=41366"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/categories?post=41366"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/tags?post=41366"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}