{"id":1410,"date":"2026-03-03T20:46:04","date_gmt":"2026-03-03T20:46:04","guid":{"rendered":"https:\/\/owspakistan.com\/?p=1410"},"modified":"2026-03-04T10:28:12","modified_gmt":"2026-03-04T10:28:12","slug":"ww2-fm-radio-training-video","status":"publish","type":"post","link":"https:\/\/owspakistan.com\/?p=1410","title":{"rendered":"Watch a classified FM radio training video from WW2"},"content":{"rendered":"<div>\n<section class=\"recurrent-blocks recurrent-newsletter-block recurrent-newsletter-email-block recurrent-newsletter-email-block-on-top pw-incontent-excluded flipboard-remove \">\n<div class=\"container newsletter-container\">\n<div class=\"newsletter-content\">\n<h2 class=\"newsletter-cta-title\"> <\/h2>\n<p class=\"article-paragraph skip\">Get the Popular Science daily newsletter\ud83d\udca1<\/p>\n<div class=\"newsletter-cta-description\">\n<p class=\"article-paragraph skip\"><span style=\"font-weight: 400\">Breakthroughs, discoveries, and DIY tips sent six days a week.<\/span><\/p>\n<\/p><\/div><\/div><\/div>\n<\/section>\n<p class=\"pw-incontent-excluded article-paragraph skip\">It\u2019s worth remembering that one of today\u2019s most commonplace pieces of <a href=\"https:\/\/www.popsci.com\/category\/technology\/\" target=\"_blank\" rel=\"noopener\">technology<\/a> frequently confounded the public when it first hit the marker. While fewer and fewer people are listening to FM radio today, it was hot stuff amid its widespread rollout during the late 1930s and early 40s. Short for frequency modulation, FM\u2019s appeal compared to <a href=\"https:\/\/www.popsci.com\/technology\/congress-am-radio\/\" target=\"_blank\" rel=\"noopener\">AM<\/a> (amplitude modulation) were immediately apparent: a clearer sound, less static, and more reliable transmissions.<\/p>\n<p class=\"article-paragraph skip\">While most audiences only cared about the improved radio experience, understanding FM\u2019s technicalities was crucial if you were expected to rely on it during actual life-or-death situations. The matter was so serious during World War II that the United States government funded a classified, 30-minute educational video in 1944 for its armed forces called \u201c<a href=\"https:\/\/www.youtube.com\/watch?v=AzvxefRDT84\" rel=\"nofollow noreferrer noopener\" target=\"_blank\">Basic Principles of Frequency Modulation<\/a>.\u201d\u00a0<\/p>\n<p class=\"article-paragraph skip\">Prior to FM, the military transmitted a lot of its communications through AM frequencies that are highly susceptible to static interference.\u00a0<\/p>\n<p class=\"article-paragraph skip\">\u201cFrequency modulation licks this problem, and that\u2019s why we want you to know something about it,\u201d a square-jawed army actor informs viewers early on in the movie.<\/p>\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio wp-embed-aspect-16-9 wp-has-aspect-ratio is-lazied\">\n<div class=\"lazied-youtube-frame\" data-video-id=\"AzvxefRDT84\" data-start-time=\"0\" data-iframe-classes=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio wp-embed-aspect-16-9 wp-has-aspect-ratio\">\n\t\t<img decoding=\"async\" class=\"lazied-youtube-frame-thumbnail\" loading=\"lazy\" src=\"https:\/\/i.ytimg.com\/vi\/AzvxefRDT84\/hqdefault.jpg\"\/><\/p>\n<p>\n\t\t\t\t\u201cBASIC PRINCIPLES OF FREQUENCY MODULATION\u201d   1944 U.S. WAR DEPARTMENT FILM FM RADIO 86794\t\t\t<\/p>\n<p>\t\t<svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"lazied-youtube-frame-icon\" viewbox=\"0 0 68 48\">\n\t\t\t<path d=\"M66.52 7.74c-.78-2.93-2.49-5.41-5.42-6.19C55.79.13 34 0 34 0S12.21.13 6.9 1.55c-2.93.78-4.63 3.26-5.42 6.19C.06 13.05 0 24 0 24s.06 10.95 1.48 16.26c.78 2.93 2.49 5.41 5.42 6.19C12.21 47.87 34 48 34 48s21.79-.13 27.1-1.55c2.93-.78 4.64-3.26 5.42-6.19C67.94 34.95 68 24 68 24s-.06-10.95-1.48-16.26z\" fill=\"red\"\/>\n\t\t\t<path d=\"M45 24 27 14v20\" fill=\"white\"\/>\n\t\t<\/svg>\n\t<\/div>\n<\/figure>\n<p><noscript><\/p>\n<p><iframe title=\"\u201cBASIC PRINCIPLES OF FREQUENCY MODULATION\u201d   1944 U.S. WAR DEPARTMENT FILM FM RADIO 86794\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/AzvxefRDT84?feature=oembed\" 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<p><\/noscript><\/p>\n<p class=\"article-paragraph skip\">To <a href=\"https:\/\/www.popsci.com\/technology\/am-radio-electric-vehicles\/\" target=\"_blank\" rel=\"noopener\">send messages with AM<\/a>, an oscillator first generates a carrier wave that feeds into an amplifier. Audio from a microphone is then funneled into a modulator as electrical energy before it heads to the amplifier. From there, the energy is pressed onto the wave and beamed out to receivers. The problem with AM is that information is transmitted based on the strength of its carrier, making it highly susceptible to a range of electrical interferences. As the film illustrates at the outset, even something as simple as a nearby electric razor is enough to create static on AM radio.\u00a0<\/p>\n<p class=\"article-paragraph skip\">\u201cFrequency modulation, or FM, is a big step forward in radio. When you tune in, you hear what the studio mic hears,\u201d the narrator proclaims.<\/p>\n<p class=\"article-paragraph skip\">With FM, a carrier wave uses frequency instead of its amplitude so that static only affects the amplitude This means that any interference simply mucks with the portion of the signal that doesn\u2019t carry the message.<\/p>\n<p class=\"article-paragraph skip\">It may feel a bit hokey and outdated in 2026, but as <a href=\"https:\/\/boingboing.net\/2026\/03\/02\/the-war-departments-1944-guide-to-fm-radio-is-still-a-great-explainer.html\" rel=\"noreferrer noopener\" target=\"_blank\">BoingBoing<\/a> recently highlighted, the movie still provides an impressively concise breakdown of radiowaves, as well as discriminators, limiters, modulators, and oscillators.<\/p>\n<p class=\"article-paragraph skip\">\u201cWhen frequency modulation is used, you can be sure that electrical interference won\u2019t hash up your messages,\u201d promises the training video\u2019s host.<\/p>\n<p class=\"article-paragraph skip\">Roger that, sir.<\/p>\n<section class=\"content-widget content-widget--large pw-incontent-excluded\">\n<p>\t<span class=\"block bg-secondary-300 h-2 w-16 mt-10 mb-8\">\u00a0<\/span><\/p>\n<div class=\"flex flex-col md:flex-row items-start justify-items-start\">\n<div class=\"mb-4 md:mb-0 md:w-4\/12 w-full\">\n\t\t\t\t<img decoding=\"async\" width=\"300\" height=\"169\" src=\"https:\/\/www.popsci.com\/wp-content\/uploads\/2025\/12\/best-of-whats-new-2025-HERO.png?quality=85&amp;w=300\" class=\"max-w-[100%]\" alt=\"products on a page that says best of what's new 2025\" srcset=\"https:\/\/www.popsci.com\/wp-content\/uploads\/2025\/12\/best-of-whats-new-2025-HERO.png?w=50&amp;h=28 50w, https:\/\/www.popsci.com\/wp-content\/uploads\/2025\/12\/best-of-whats-new-2025-HERO.png?w=280&amp;h=158 280w, https:\/\/www.popsci.com\/wp-content\/uploads\/2025\/12\/best-of-whats-new-2025-HERO.png?w=289&amp;h=163 289w\" sizes=\"(max-width: 300px) 100vw, 300px\"\/>\t\t\t<\/div>\n<div class=\"ml-0 md:ml-10 md:w-8\/12 w-full\">\n<h3 class=\"wp-block-heading\">\n\t\t\t\t<\/h3>\n<p>2025 PopSci Best of What\u2019s New<\/p>\n<div class=\"content-widget-content mb-4\">\n<div id=\"1737663310.940689\" class=\"c-virtual_list__item\" role=\"listitem\" data-qa=\"virtual-list-item\" data-item-key=\"1737663310.940689\">\n<div class=\"c-message_kit__background c-message_kit__background--hovered p-message_pane_message__message c-message_kit__message\" role=\"presentation\" data-qa=\"message_container\" data-qa-unprocessed=\"false\" data-qa-placeholder=\"false\">\n<div class=\"c-message_kit__hover c-message_kit__hover--hovered\" role=\"document\" data-qa-hover=\"true\">\n<div class=\"c-message_kit__actions c-message_kit__actions--above\">\n<div class=\"c-message_kit__gutter\">\n<div class=\"c-message_kit__gutter__right\" role=\"presentation\" data-qa=\"message_content\">\n<div class=\"c-message_kit__blocks c-message_kit__blocks--rich_text\">\n<div class=\"c-message__message_blocks c-message__message_blocks--rich_text\" data-qa=\"message-text\">\n<div class=\"p-block_kit_renderer\" data-qa=\"block-kit-renderer\">\n<div class=\"p-block_kit_renderer__block_wrapper p-block_kit_renderer__block_wrapper--first\">\n<div class=\"p-rich_text_block\" dir=\"auto\">\n<div class=\"p-rich_text_section\">\n<p class=\"article-title\">The 50 most important innovations of the year<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div><\/div><\/div><\/div>\n<p>\t<span class=\"block bg-secondary-300 h-2 w-16 mt-8 mb-10\">\u00a0<\/span><\/p>\n<\/section>\n<footer class=\"article-content-footer lg:max-w-[730px] lg:mx-auto\">\n<div class=\"pw-incontent-excluded\">\n<section id=\"author-widgets\" class=\"recurrent-author-widgets pw-incontent-excluded\">\n<section class=\"recurrent-author-widget recurrent-primary-author-widget pw-incontent-excluded\">\n<div class=\"author-bio pw-incontent-excluded\">\n<p>Andrew Paul is a staff writer for Popular Science.<\/p>\n<\/div>\n<\/section>\n<hr class=\"author-divider\"\/>\n\t\t\t\t\t\t\t\t\t\t\t<\/section><\/div>\n<\/footer><\/div>\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Get the Popular Science daily newsletter\ud83d\udca1 Breakthroughs, discoveries, and DIY tips sent six days a week. It\u2019s worth remembering that one of today\u2019s most commonplace pieces of technology frequently confounded the public when it first hit the marker. While fewer and fewer people are listening to FM radio today, it was hot stuff amid its<\/p>\n","protected":false},"author":1,"featured_media":1411,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[253,254,109],"tags":[95,96,89],"class_list":["post-1410","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-engineering","category-military","category-technology","tag-culture","tag-history","tag-news"],"jetpack_publicize_connections":[],"_links":{"self":[{"href":"https:\/\/owspakistan.com\/index.php?rest_route=\/wp\/v2\/posts\/1410","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/owspakistan.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/owspakistan.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/owspakistan.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/owspakistan.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1410"}],"version-history":[{"count":0,"href":"https:\/\/owspakistan.com\/index.php?rest_route=\/wp\/v2\/posts\/1410\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/owspakistan.com\/index.php?rest_route=\/wp\/v2\/media\/1411"}],"wp:attachment":[{"href":"https:\/\/owspakistan.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1410"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/owspakistan.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1410"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/owspakistan.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1410"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}