{"id":91,"date":"2023-01-23T22:48:14","date_gmt":"2023-01-23T21:48:14","guid":{"rendered":"http:\/\/sp5tof.vxm.pl\/?page_id=91"},"modified":"2025-11-21T19:00:06","modified_gmt":"2025-11-21T18:00:06","slug":"direct-sampling-mode-in-820t2-dvb-t-on-linux-os","status":"publish","type":"post","link":"https:\/\/sp5tof.pl\/?p=91","title":{"rendered":"Direct Sampling Mode in 820T2 DVB-T on Linux os"},"content":{"rendered":"<p>Dear OMs,<\/p>\n<p>As you know, the DVB-T Receiver 820T2 can be physically modified and be able to receives low ham radio frequencies (f.ex. 1.8 &#8211; 14MHz). This is what I&#8217;m talking about :<\/p>\n<p><iframe loading=\"lazy\" src=\"https:\/\/www.youtube.com\/embed\/lrwThfWL8Mw\" width=\"560\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>Everything looks fine in case of Windows, but in case of Linux system and rtl_tcp service, some issue can occure.<br \/>\nHere you can find the youtube movie about RTL-SDR driver installation within Linux environment:<\/p>\n<p><iframe loading=\"lazy\" src=\"https:\/\/www.youtube.com\/embed\/hM3DwMjIGvs\" width=\"560\" height=\"315\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p>Here you can also find a short but very usefull briefly description:<\/p>\n<p><a href=\"http:\/\/drwxr.org\/2016\/10\/installing-rtl-sdr-rtl2832u-driver\/\" target=\"_blank\" rel=\"noopener\">installing-rtl-sdr-rtl2832u-driver<\/a><\/p>\n<p>I modified the source code and equipped it with the &#8220;-i&#8221; parameter, which allow you to point out the &#8220;I&#8221; or &#8220;Q&#8221; channel of your dongle when the &#8220;rtl_tcp&#8221; deamon is started.<br \/>\nWhat is more, I also added a possibility to change the AGC mode( -c option), which is turned on by default. In case of any WebSDR, enabling the AGC could leads to unexpectable muting of weaker stations.<\/p>\n<p>How to implement it? I would recommend the procedure from the link above with step 5 to be modified as following:<\/p>\n<pre><span style=\"color: #000000;\">git clone git:\/\/git.osmocom.org\/rtl-sdr.git\r\n\r\ncd rtl-sdr\/\r\n\r\nmkdir build\r\n\r\ncd build\r\n\r\n<strong>{now here is the trick: please replace the \r\nrtl-sdr\/src\/rtl_tcp.c <\/strong><strong>with a file downloaded and unpacked \r\nfrom archive available on the bottom of this site<\/strong><strong>}<\/strong>\r\n\r\ncmake ..\/ -DINSTALL_UDEV_RULES=ON\r\n\r\nmake\r\n\r\nsudo make install\r\n\r\nsudo ldconfig\r\n\r\nsudo cp ..\/rtl-sdr.rules \/etc\/udev\/rules.d\/<\/span><\/pre>\n<p>When these steps are done you will be able to see the additional options within the rtl_tcp deamon(you can chek it out by typing rtl_tcp &#8211;help command:<\/p>\n<pre><span style=\"color: #000000;\">rtl_tcp, an I\/Q spectrum server for RTL2832 based DVB-T receivers\r\nModified by Jakub\/SP5TOF on 07.02.2017 for direct sampling support\r\n\r\nUsage: [-a listen address]\r\n [-p listen port (default: 1234)]\r\n [-f frequency to tune to [Hz]]\r\n [-g gain (default: 0 for auto)]\r\n [-s samplerate in Hz (default: 2048000 Hz)]\r\n [-b number of buffers (default: 32, set by library)]\r\n [-n max number of linked list buffers to keep (default: 500)]\r\n [-d device index (default: 0)]\r\n [-P ppm_error (default: 0)]\r\n [-i direct sampling(1: I-ADC input enabled), 2: Q-ADC input enabled)]\r\n [-c AGC Mode(1: ON, 0: OFF), default: 1(ON)\r\n<\/span><\/pre>\n<p><strong><span style=\"color: #ffffff;\">Example:<\/span><\/strong><\/p>\n<p><strong><span style=\"color: #ffffff;\">rtl_tcp -i 1 -c 0 -g 49.6<\/span><\/strong><\/p>\n<p>By typing the command above, you will be able to launch the rtl_tcp deamon with support of hardware mod for direct sampling(the RF input can be directly connected to the I pad on the dongle&#8217;s PCB).<\/p>\n<p><b>PLEASE BE AWARE THAT IT WORKS ONLY WITH RTL-SDR-0.5.3 DRIVER!<\/b><br \/>\nIn case of any further driver releases comes from GIT, provided file will has to be rewritten!<\/p>\n<h5>Please find the file : <a href=\"https:\/\/sp5tof.pl\/wp-content\/uploads\/2023\/01\/rtl_tcp.zip\">rtl_tcp<\/a><\/h5>\n<p style=\"text-align: right;\">Jakub\/SP5TOF<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Dear OMs, As you know, the DVB-T Receiver 820T2 can be physically modified and be able to receives low ham radio frequencies (f.ex. 1.8 &#8211; 14MHz). This is what I&#8217;m&hellip; <\/p>\n","protected":false},"author":1,"featured_media":717,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[5],"tags":[],"class_list":["post-91","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-radio"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/posts\/91","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=91"}],"version-history":[{"count":12,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/posts\/91\/revisions"}],"predecessor-version":[{"id":104,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/posts\/91\/revisions\/104"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=\/wp\/v2\/media\/717"}],"wp:attachment":[{"href":"https:\/\/sp5tof.pl\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=91"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=91"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sp5tof.pl\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=91"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}