{"id":51812,"date":"2022-02-08T10:03:31","date_gmt":"2022-02-08T14:03:31","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=51812"},"modified":"2022-02-08T10:03:31","modified_gmt":"2022-02-08T14:03:31","slug":"guest-post-control-of-electromagnetic-radiation-conelrad","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2022\/02\/guest-post-control-of-electromagnetic-radiation-conelrad\/","title":{"rendered":"Guest Post: Control of Electromagnetic Radiation (CONELRAD)"},"content":{"rendered":"

\"\"<\/a><\/p>\n

Many thanks to SWLing Post contributor,\u00a0Bob Colegrove<\/a>, who shares the following guest post:<\/strong><\/em><\/p>\n

\n

Control of Electromagnetic Radiation (CONELRAD)<\/b><\/h1>\n

As recalled by Bob Colegrove<\/strong><\/p>\n

In his comment on my recent posting, Tinkering with History<\/i><\/a>, Mario noted the dial on the featured radio, the General Electric P755A, sported two small triangles, one between 6 and 7, and the other between 11 and 14.\u00a0 He noted that these were civil defense markers intended to show the frequencies of 640 kHz and 1240 kHz, respectively, and that these were characteristic of AM radios produce in the US roughly between 1953 and 1963.\u00a0 Since two full generations have been born and raised to adulthood since that time, and I can\u2019t find any related posting here, I thought it might be useful to bring this subject to light.<\/p>\n

\"\"<\/a><\/p>\n

In spite of otherwise economic prosperity and general wellbeing, these years were nevertheless filled with anxiety about the prospects of all-out war.\u00a0 Children of the time (myself included) were being shown how to hide under their school desks, and some of their parents were going so far as to construct air-raid shelters in their basements, and stock them with enough provisions to supposedly outlast any catastrophe.\u00a0 So it was that CONELRAD came into being in 1951.\u00a0 The idea was, that in case of a National emergency, all radio and TV stations would go off the air, and only certain medium wave radio stations would stay on either 640 kHz or 1240 kHz.\u00a0 They would remain on for a few minutes and then other stations would take over in a round robin arrangement \u2013 this to deter homing by hostile bombers.\u00a0 Needless to say, quickly changing over transmitters and antennas to one of these two frequencies did not bode well for the equipment and there were many failures in subsequent tests.\u00a0 Note that, as originally conceived, the system did not provide for local weather emergencies or other situations.<\/p>\n

\"\"<\/a><\/p>\n

The banner photo at the top of this posting shows a portion of the Hallicrafters S-38E receiver which conformed to Government law of the time required for marking all AM dials.\u00a0 An S-38E just like it was my first genuine multi-band radio in 1959.\u00a0 Assuming good alignment, the dots next to the CD triangles indicated the 640 kHz and 1240 kHz frequencies.\u00a0 When a test came on, you didn\u2019t have to fish for it, since CONELRAD was the only service transmitting.<\/p>\n

Going back to the radios described in Tinkering with History<\/a><\/i>, GE took this one step further.\u00a0 The figure below shows a portion of the dial on a GE P806A.\u00a0 Note the nub on the outer edge of the dial under the triangle at 1240 kHz.\u00a0 There is another nub on the edge at 640 kHz.\u00a0 Together with the raised triangular dial pointer molded on the cabinet, they provided a braille system, so that someone visually impaired could easily tune to a CONELRAD frequency.<\/p>\n

\"\"<\/a><\/p>\n

As technology improved, CONELRAD transitioned to the Emergency Broadcast System (EBS) in 1963, and subsequently the Emergency Alert System in 1997.\u00a0 A more thorough description of CONELRAD can be found on Wikipedia https:\/\/en.wikipedia.org\/wiki\/CONELRAD<\/a>.\u00a0 Reprint of an April 1955 Radio & Television News<\/i> article describing the construction of a transistor CONELRAD receiver is at https:\/\/www.rfcafe.com\/references\/radio-news\/conelrad-radio-television-news-april-1955.htm<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Many thanks to SWLing Post contributor,\u00a0Bob Colegrove, who shares the following guest post: Control of Electromagnetic Radiation (CONELRAD) As recalled by Bob Colegrove In his comment on my recent posting, Tinkering with History, Mario noted the dial on the featured radio, the General Electric P755A, sported two small triangles, one between 6 and 7, and […]<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"closed","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":[373,3194,433,3,288,4796],"tags":[625,7988,752,9654,9655,4342,681],"class_list":["post-51812","post","type-post","status-publish","format-standard","hentry","category-am","category-guest-posts","category-mediumwave","category-news","category-radio-history","category-vintage-radio","tag-am-radio","tag-bob-colegrove","tag-cold-war","tag-conelrad","tag-control-of-electromagnetic-radiation-conelrad","tag-guest-posts","tag-vintage-radio"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pn3uc-dtG","jetpack-related-posts":[{"id":49864,"url":"https:\/\/swling.com\/blog\/2021\/08\/bob-colegrove-on-the-joys-and-challenges-of-tuning-analog-radios\/","url_meta":{"origin":51812,"position":0},"title":"Bob Colegrove on “The Joys and Challenges of Tuning Analog Radios”","author":"Thomas","date":"August 1, 2021","format":false,"excerpt":"Many thanks to SWLing Post contributor, Bob Colegrove, who recently shared this excellent article and has kindly allowed me to share it here in the the Post. Bob prefaced it by saying, \"Being a retired technical writer, I started the attached article some time ago for my own amusement, but\u2026","rel":"","context":"In "Books"","block_context":{"text":"Books","link":"https:\/\/swling.com\/blog\/category\/books\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/08\/Bob-Colegrove-Book-1.jpeg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/08\/Bob-Colegrove-Book-1.jpeg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/08\/Bob-Colegrove-Book-1.jpeg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2021\/08\/Bob-Colegrove-Book-1.jpeg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":56447,"url":"https:\/\/swling.com\/blog\/2023\/04\/bobs-bespoke-rack-of-radios\/","url_meta":{"origin":51812,"position":1},"title":"Bob’s Bespoke “Rack of Radios”","author":"Thomas","date":"April 24, 2023","format":false,"excerpt":"Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following: A Rack of Radios by Bob Colegrove You simply cannot have enough radios \u2013 a principle I learned a long time ago.\u00a0 The difficulty occurs when it comes to storing them and yet having them at the ready\u2026","rel":"","context":"In "Accessories"","block_context":{"text":"Accessories","link":"https:\/\/swling.com\/blog\/category\/accessories\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/04\/image1-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/04\/image1-1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/04\/image1-1.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/04\/image1-1.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2023\/04\/image1-1.jpg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":60370,"url":"https:\/\/swling.com\/blog\/2024\/08\/a-band-aid-for-the-xhdata-d-220\/","url_meta":{"origin":51812,"position":2},"title":"A Band Aid for the XHDATA D-220","author":"Thomas","date":"August 11, 2024","format":false,"excerpt":"Many thanks to\u00a0SWLing Post\u00a0contributor, Bob Colegrove, who shares the following guest post: A Band Aid for the XHDATA D-220 By Bob Colegrove In the olden days of analog radios, we would have generated a graph plotting frequency against a 0 to 100 linear bandspread scale. That permitted determination of a\u2026","rel":"","context":"In "Guest Posts"","block_context":{"text":"Guest Posts","link":"https:\/\/swling.com\/blog\/category\/guest-posts\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Fig-1.jpeg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Fig-1.jpeg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Fig-1.jpeg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Fig-1.jpeg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Fig-1.jpeg?resize=1050%2C600&ssl=1 3x"},"classes":[]},{"id":60460,"url":"https:\/\/swling.com\/blog\/2024\/08\/u-twente-websdr-new-tablet-phone-interface-option\/","url_meta":{"origin":51812,"position":3},"title":"U Twente WebSDR: New Tablet\/Phone Interface Option","author":"Thomas","date":"August 25, 2024","format":false,"excerpt":"Many thanks to\u00a0SWLing Post\u00a0contributor,\u00a0Bob Colegrove, who shares the following guest post: U. of Twenty Site for Phones and Tablets by Bob Colegrove I\u2019m not sure if this is new.\u00a0 It may have been around for a while.\u00a0 Very recently, while accessing the WebSDR site at the University of Twente, it\u2026","rel":"","context":"In "News"","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\/2024\/08\/Figure.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Figure.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/08\/Figure.png?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":39419,"url":"https:\/\/swling.com\/blog\/2019\/09\/guest-post-the-national-association-of-armchair-adventurers-naaa\/","url_meta":{"origin":51812,"position":4},"title":"Guest Post: The National Association of Armchair Adventurers (NAAA)","author":"Thomas","date":"September 3, 2019","format":false,"excerpt":"Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following guest post: National Association of Armchair Adventurers (NAAA) as recalled by Bob Colegrove Those of you who were into SWLing in the late \u201850s or early \u201860s may remember the NAAA.\u00a0 It was an engaging promotional effort by\u2026","rel":"","context":"In "News"","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\/2018\/07\/Radio-Dial-1024x679.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2018\/07\/Radio-Dial-1024x679.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2018\/07\/Radio-Dial-1024x679.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":61368,"url":"https:\/\/swling.com\/blog\/2024\/12\/bobs-1968-radio-tirana-qsl-card\/","url_meta":{"origin":51812,"position":5},"title":"Bob’s 1968 Radio Tirana QSL Card","author":"Thomas","date":"December 12, 2024","format":false,"excerpt":"Many thanks to SWLing Post contributor Bob Colegrove, who writes: Kudos to Don Moore for his excellently crafted article on Albanian radio. [...]Perhaps some might be interested to see a 1968 QSL from R. Tirana. Regards, Bob Colegrove Thank you for sharing this excellent Radio Tirana QSL card, Bob!","rel":"","context":"In "News"","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\/2024\/12\/R-Tirana-Inside.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/12\/R-Tirana-Inside.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/12\/R-Tirana-Inside.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/12\/R-Tirana-Inside.jpg?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2024\/12\/R-Tirana-Inside.jpg?resize=1050%2C600&ssl=1 3x"},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts\/51812","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=51812"}],"version-history":[{"count":0,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/posts\/51812\/revisions"}],"wp:attachment":[{"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/media?parent=51812"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/categories?post=51812"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/swling.com\/blog\/wp-json\/wp\/v2\/tags?post=51812"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}