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13All About Trunk Recorder</h1><h2 class="anchor anchorWithStickyNavbar_LWe7" id="sponsors">Sponsors<a href="#sponsors" class="hash-link" aria-label="Direct link to Sponsors" title="Direct link to Sponsors">â</a></h2><p><strong>Do you find Trunk Recorder and OpenMHz useful?</strong> 14Become a <a href="https://github.com/sponsors/robotastic" target="_blank" rel="noopener noreferrer">Sponsor</a> to help support continued development and operation! 15Thank you to everyone who has contributed!</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="overview">Overview<a href="#overview" class="hash-link" aria-label="Direct link to Overview" title="Direct link to Overview">â</a></h2><p>Need help? Got something working? Share it!</p><p><a href="https://discord.gg/btJAhESnks" target="_blank" rel="noopener noreferrer">Discord Server</a> - and don't forget the <a href="https://github.com/TrunkRecorder/trunk-recorder/wiki" target="_blank" rel="noopener noreferrer">Wiki</a></p><p>Trunk Recorder is able to record the calls on trunked and conventional radio systems. It uses 1 or more Software Defined Radios (SDRs) to do this. The SDRs capture large swathes of RF and then use software to process what was received. <a href="https://gnuradio.org/" target="_blank" rel="noopener noreferrer">GNU Radio</a> is used to do this processing because it provides lots of convenient RF blocks that can be pieced together to allow for complex RF processing. The libraries from the amazing <a href="http://op25.osmocom.org/trac/wiki" target="_blank" rel="noopener noreferrer">OP25</a> project are used for a lot of the P25 functionality. Multiple radio systems can be recorded at the same time.</p><p>Trunk Recorder currently supports the following:</p><ul><li>Trunked P25 & SmartNet Systems</li><li>Conventional P25 & analog systems, where each group has a dedicated RF channel</li><li>P25 Phase 1, P25 Phase 2 & Analog voice channels</li></ul><p>Supported platforms:</p><p><strong>Ubuntu</strong> (18.04, 20.04, 21.04, 22.04, 23.04); <strong>Raspberry Pi</strong> (Raspberry OS/Raspbian & Ubuntu 21.04, 22.04); <strong>Arch Linux</strong> (2021.09.20); <strong>Debian</strong> (9.x); <strong>macOS</strong></p><p>GNU Radio 3.7 - 3.10</p><p>...and SDRs:</p><p>RTL-SDR dongles; HackRF; Ettus USRP B200, B210, B205; BladeRF; Airspy</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="install">Install<a href="#install" class="hash-link" aria-label="Direct link to Install" title="Direct link to Install">â</a></h2><h3 class="anchor anchorWithStickyNavbar_LWe7" id="linux">Linux<a href="#linux" class="hash-link" aria-label="Direct link to Linux" title="Direct link to Linux">â</a></h3><ul><li><a href="/docs/Install/INSTALL-DOCKER">Docker</a> </li><li><a href="/docs/Install/INSTALL-LINUX">From Source</a></li></ul><h3 class="anchor anchorWithStickyNavbar_LWe7" id="raspberry-pi">Raspberry Pi<a href="#raspberry-pi" class="hash-link" aria-label="Direct link to Raspberry Pi" title="Direct link to Raspberry Pi">â</a></h3><ul><li><a href="/docs/Install/INSTALL-DOCKER">Docker</a> </li><li><a href="/docs/Install/INSTALL-PI">From Source</a> - <a href="https://youtu.be/DizBtDZ6kE8" target="_blank" rel="noopener noreferrer">Video Walkthrough</a></li></ul><h3 class="anchor anchorWithStickyNavbar_LWe7" id="macos">MacOS<a href="#macos" class="hash-link" aria-label="Direct link to MacOS" title="Direct link to MacOS">â</a></h3><ul><li><a href="/docs/Install/INSTALL-MAC#using-homebrew">From Source</a></li></ul><h2 class="anchor anchorWithStickyNavbar_LWe7" id="setup">Setup<a href="#setup" class="hash-link" aria-label="Direct link to Setup" title="Direct link to Setup">â</a></h2><ul><li><a href="/docs/CONFIGURE">Configuring a system</a></li><li><a href="/docs/FAQ">FAQ</a></li></ul><h3 class="anchor anchorWithStickyNavbar_LWe7" id="troubleshooting">Troubleshooting<a href="#troubleshooting" class="hash-link" aria-label="Direct link to Troubleshooting" title="Direct link to Troubleshooting">â</a></h3><p>If are having trouble, check out the <a href="/docs/FAQ">FAQ</a> and/or ask a question on the <a href="https://discord.gg/btJAhESnks" target="_blank" rel="noopener noreferrer">Discord Server</a> </p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="how-trunking-works">
15How Trunking Works<a href="#how-trunking-works" class="hash-link" aria-label="Direct link to How Trunking Works" title="Direct link to How Trunking Works">â</a></h2><p>For those not familiar, trunking systems allow a large number of user groups to share a limited number of radio frequencies by temporarily, dynamically assigning radio frequencies to talkgroups (channels) on-demand. It is understood that most user groups actually use the radio very sporadically and don't need a dedicated frequency. </p><p>Most trunking system types (such as SmartNet and P25) set aside one of the radio frequencies as a "control channel" that manages and broadcasts radio frequency assignments. When someone presses the Push to Talk button on their radio, the radio sends a message to the system which then assigns a voice frequency and broadcasts a Channel Grant message about it on the control channel. This lets the radio know what frequency to transmit on and tells other radios set to the same talkgroup to listen.</p><p>In order to follow all of the transmissions, Trunk Recorder constantly listens to and decodes the control channel. When a frequency is granted to a talkgroup, Trunk Recorder creates a monitoring process which decodes the portion of the radio spectrum for that frequency from the SDR that is already pulling it in.</p><p>No message is transmitted on the control channel when a conversation on a talkgroup is over. The monitoring process keeps track of transmissions and if there has been no activity for a specified period, it ends the recording.</p></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="theme-doc-footer-edit-meta-row row"><div class="col"><a href="https://github.com/TrunkRecorder/trunkrecorder.github.io/tree/main/docs/intro.md" target="_blank" rel="noreferrer noopener" class="theme-edit-this-page"><svg fill="currentColor" height="20" width="20" viewBox="0 0 40 40" class="iconEdit_Z9Sw" aria-hidden="true"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col lastUpdated_vwxv"></div></div></footer></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--next" href="/docs/Install/INSTALL-LINUX"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Linux Install</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#sponsors" class="table-of-contents__link toc-highlight">Sponsors</a></li><li><a href="#overview" class="table-of-contents__link toc-highlight">Overview</a></li><li><a href="#install" class="table-of-contents__link toc-highlight">Install</a><ul><li><a href="#linux" class="table-of-contents__link toc-highlight">Linux</a></li><li><a href="#raspberry-pi" class="table-of-contents__link toc-highlight">Raspberry Pi</a></li><li><a href="#macos" class="table-of-contents__link toc-highlight">MacOS</a></li></ul></li><li><a href="#setup" class="table-of-contents__link toc-highlight">Setup</a><ul><li><a href="#troubleshooting" class="table-of-contents__link toc-highlight">Troubleshooting</a></li></ul></li><li><a href="#how-trunking-works" class="table-of-contents__link toc-highlight">How Trunking Works</a></li></ul></div></div></div></div></main></div></div><footer class="footer footer--dark"><div class="container container-fluid"><div class="row footer__links"><div class="col footer__col"><div class="footer__title">Docs</div><ul class="footer__items clean-list"><li class="footer__item"><a class="footer__link-item" href="/docs/intro">Install</a></li><li class="footer__item"><a class="footer__link-item" href="/docs/intro">Configure</a></li></ul></div><div class="col footer__col"><div class="footer__title">Community</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://github.com/sponsors/robotastic" target="_blank" rel="noopener noreferrer" class="footer__link-item">Sponsor<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU">
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