{"id":3898,"date":"2024-12-01T14:32:54","date_gmt":"2024-12-01T19:32:54","guid":{"rendered":"https:\/\/dft.wiki\/?p=3898"},"modified":"2026-06-08T10:24:50","modified_gmt":"2026-06-08T14:24:50","slug":"software-defined-radio-reference-guide","status":"publish","type":"post","link":"https:\/\/dft.wiki\/?p=3898","title":{"rendered":"Software Defined Radio (SDR) Reference Guide"},"content":{"rendered":"<p><strong>INDEX<\/strong><\/p>\n<ul>\n<li>Briefing<\/li>\n<li>Spectrum<\/li>\n<li>Antennas and Filters<\/li>\n<li>Antenna Types<\/li>\n<li>Wavelength Calculator<\/li>\n<li>Frequency Calculator<\/li>\n<\/ul>\n<hr \/>\n<p><strong>BRIEFING<\/strong><\/p>\n<p>Software-defined radio (SDR) is a technology that replaces traditional hardware-based radio components with software.<\/p>\n<p>This post is not meant to be an encyclopedia on SDR, but a landing page with links and references to the most important resources for getting started in the field.<\/p>\n<p>I use the official kit &#8220;RTL-SDR Blog V4 RTL2832 1PPM TCXO HF BiasT SMA Software Defined Radio + Antennas&#8221; [<a href=\"https:\/\/www.rtl-sdr.com\/V4\/\">Link<\/a>]. Follow along with the vendor&#8217;s &#8220;Quick Install Guide&#8221; [<a href=\"https:\/\/www.rtl-sdr.com\/rtl-sdr-quick-start-guide\/\">Link<\/a>].<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-3899 size-medium\" src=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/01\/Screenshot-from-2024-01-20-09-55-31-300x226.png\" alt=\"\" width=\"300\" height=\"226\" srcset=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/01\/Screenshot-from-2024-01-20-09-55-31-300x226.png 300w, https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/01\/Screenshot-from-2024-01-20-09-55-31-768x578.png 768w, https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/01\/Screenshot-from-2024-01-20-09-55-31.png 801w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>Datasheet source [<a href=\"https:\/\/www.rtl-sdr.com\/wp-content\/uploads\/2024\/12\/RTLSDR_V4_Datasheet_V_1_0.pdf\">Link<\/a>].<\/p>\n<table align=\"center\">\n<caption><strong>Features Summary<\/strong><\/caption>\n<tbody>\n<tr>\n<td>Tuner Chip<\/td>\n<td>R828D<\/td>\n<\/tr>\n<tr>\n<td>ADC Chip<\/td>\n<td>RTL2832U 8-bits<\/td>\n<\/tr>\n<tr>\n<td>Frequency Range<\/td>\n<td>500 kHz to 1.766 GHz<\/td>\n<\/tr>\n<tr>\n<td>Bandwidth<\/td>\n<td>2.56 MHz stable (up to 3.2 MHz with drops)<\/td>\n<\/tr>\n<tr>\n<td>Typical Input Impedance<\/td>\n<td>50 Ohms<\/td>\n<\/tr>\n<tr>\n<td>Typical Current Draw<\/td>\n<td>250 to 270 mA<\/td>\n<\/tr>\n<tr>\n<td>HF Implementation<\/td>\n<td>Upconverter with 28.8 MHz LO<\/td>\n<\/tr>\n<tr>\n<td>Input Connector<\/td>\n<td>1x SMA<\/td>\n<\/tr>\n<tr>\n<td>USB Connector<\/td>\n<td>USB-A Male<\/td>\n<\/tr>\n<tr>\n<td>Local Oscillator Stability<\/td>\n<td>1PPM TCXO<\/td>\n<\/tr>\n<tr>\n<td>Bias Tee<\/td>\n<td>4.5V, 180mA (software switchable)<\/td>\n<\/tr>\n<tr>\n<td>Enclosure<\/td>\n<td>Aluminum<\/td>\n<\/tr>\n<tr>\n<td>Heat Dissipation<\/td>\n<td>Thermal Pad to Aluminum Enclosure<\/td>\n<\/tr>\n<tr>\n<td>Front-End RF Design<\/td>\n<td>Triplexor with switchable notch<\/td>\n<\/tr>\n<tr>\n<td>Transmit Capability<\/td>\n<td>None<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<hr \/>\n<p><strong>SPECTRUM FOR THIS HARDWARE<\/strong><\/p>\n<table align=\"center\">\n<caption><strong>Bands and Channels<\/strong><\/caption>\n<tbody>\n<tr>\n<td>MF 500~526.5 kHz<\/td>\n<td><strong>Maritime \/ Marine<\/strong> Band<br \/>\nDistress and emergency (Morse Code), navigation<\/td>\n<\/tr>\n<tr>\n<td>MF 540~1700 kHz<\/td>\n<td><strong>AM<\/strong> Broadcasting Band<br \/>\n10 kHz steps (+\/- 5 kHz)<br \/>\nChannels: 540, 550, 560&#8230; 1700<\/td>\n<\/tr>\n<tr>\n<td>HF 3~30 MHz<\/td>\n<td>Shortwave <strong>AM<\/strong> Broadcasting Radio<\/td>\n<\/tr>\n<tr>\n<td>HF 13.56 MHz<\/td>\n<td><strong>ISM<\/strong> (Industrial, Scientific, and Medical) Band<\/td>\n<\/tr>\n<tr>\n<td>HF 27 MHz<\/td>\n<td><strong>CB<\/strong> (Citizens Band) class D:<br \/>\n10 kHz wide (AM or SSB mode)<br \/>\nUnlicensed, 40 channels: 26.965, 26.975&#8230; 27.185<\/td>\n<\/tr>\n<tr>\n<td>HF 40.68 MHz<\/td>\n<td><strong>ISM<\/strong> (Industrial, Scientific, and Medical) Band<\/td>\n<\/tr>\n<tr>\n<td>VHF 50~54 MHz<\/td>\n<td>6M <strong>HAM<\/strong> Band [<a href=\"https:\/\/www.rac.ca\/50-mhz-6m-page\/\">Link<\/a>]<\/td>\n<\/tr>\n<tr>\n<td>VHF 54~88 MHz<\/td>\n<td>Digital <strong>TV<\/strong> &#8211; Channels 2-6<\/td>\n<\/tr>\n<tr>\n<td>VHF 88~108 MHz<\/td>\n<td><strong>FM<\/strong> Broadcast Band:<br \/>\n200 kHz steps (+\/- 100 kHz)<br \/>\nChannels: 88.1 MHz, 88.3 MHz&#8230; 107.9 MHz<\/td>\n<\/tr>\n<tr>\n<td>VHF 108~137 MHz<\/td>\n<td><strong>Aviation<\/strong> Band (aka &#8220;airband&#8221;)<br \/>\nAM (legacy compatibility) or SSB mode (best)<br \/>\n108 to 117.95 MHz: 200 channels, 50 kHz steps<br \/>\n118 to 136.975 MHz: 760 channels, 25 kHz steps<\/td>\n<\/tr>\n<tr>\n<td>VHF 144~148 MHz<\/td>\n<td>2M <strong>HAM<\/strong> Band [<a href=\"https:\/\/www.rac.ca\/144-mhz-2m-page\/\">Link<\/a>]<br \/>\n<strong>ARISS-SSTV<\/strong> at 145.8 MHz NFM [<a href=\"https:\/\/ariss-sstv.blogspot.com\/\">Link<\/a>] [<a href=\"https:\/\/www.ariss.org\/current-status-of-iss-stations.html\">Link<\/a>]<\/td>\n<\/tr>\n<tr>\n<td>VHF 156~174 MHz<\/td>\n<td><strong>Marine<\/strong> Band (aka &#8220;Maritime&#8221;)<br \/>\n28 channels with 50 kHz step<br \/>\nOr 88 channels with 25 kHz steps<\/td>\n<\/tr>\n<tr>\n<td>VHF 161~161.45 MHz<\/td>\n<td><strong>Railways<\/strong> in the US and Canada<\/td>\n<\/tr>\n<tr>\n<td>VHF 162.4~162.55 MHz<\/td>\n<td><strong>NOAA Weather<\/strong> Radio (weather, alerts, and emergency)<br \/>\n8 channels, 25 kHz step, Narrow FM modulation.<br \/>\nChannels: 162.400 MHz, 162.425 MHz&#8230; 162.550 MHz<br \/>\nAlerts preceded by a 1050 Hz attention tone for 10 sec [<a href=\"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/transcoded\/7\/7d\/1050Hz_Tone.ogg\/1050Hz_Tone.ogg.mp3\">Link<\/a>]<\/td>\n<\/tr>\n<tr>\n<td>VHF 174~216 MHz<\/td>\n<td>Digital <strong>TV<\/strong> &#8211; Channels 7-13<\/td>\n<\/tr>\n<tr>\n<td>VHF 222~225 MHz<\/td>\n<td>1.35M <strong>HAM<\/strong> Band [<a href=\"https:\/\/www.rac.ca\/220-mhz-135-cm-page\/\">Link<\/a>]<\/td>\n<\/tr>\n<tr>\n<td>UHF 433 MHz<\/td>\n<td><strong>ISM<\/strong> (Industrial, Scientific, and Medical) Band<br \/>\nCentered at 433.92 MHz, channels with 25 kHz step.<\/td>\n<\/tr>\n<tr>\n<td>UHF 470~512 MHz<br \/>\nUHF 614~890 MHz<\/td>\n<td>Digital <strong>TV<\/strong><br \/>\nChannels 14-20 and 38-83 respectively.<br \/>\nChannel 37 (608~614 MHz) is reserved for radio astronomy.<\/td>\n<\/tr>\n<tr>\n<td>UHF 915 MHz<\/td>\n<td><strong>ISM<\/strong> (Industrial, Scientific, and Medical) Band<br \/>\nModulation varies by application: CSS, FSK, QAM&#8230;<br \/>\nUsage: LoRa, ZigBee, RFID, Sensors, Remotes&#8230;<\/td>\n<\/tr>\n<tr>\n<td>UHF 1227.60 MHz<br \/>\nUHF 1575.42 MHz<\/td>\n<td><strong>GNSS<\/strong> (Global Navigation Satellite System) [<a href=\"https:\/\/novatel.com\/support\/known-solutions\/gnss-frequencies-and-signals\">Link<\/a>]<br \/>\nGPS L2 and L1 frequencies respectively (BPSK modulation).<br \/>\nAlso used by Galileo (EU), GLONASS (RU), and BeiDou (CN).<\/td>\n<\/tr>\n<tr>\n<td>UHF 1660~1670 MHz<\/td>\n<td><strong>GOES<\/strong> Weather <strong>Satellite<\/strong> [<a href=\"https:\/\/www.star.nesdis.noaa.gov\/goes\">Link<\/a>]<br \/>\nTransmission of high-resolution meteorological images.<\/td>\n<\/tr>\n<tr>\n<td>UHF 1698~1707 MHz<\/td>\n<td><strong>NOAA<\/strong> Weather <strong>Satellite<\/strong> [<a href=\"https:\/\/dolphmicrowave.com\/default\/6-best-noaa-satellite-frequencies\/\">Link<\/a>]<br \/>\nTransmission of high-resolution meteorological images.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<hr \/>\n<p><strong>ANTENNAS AND FILTERS<\/strong><\/p>\n<p>The RTL-SDR kit can easily tune into FM stations out of the box, but is unlikely to receive decent-quality AM stations. The reason is that the spectrum is crowded with noise and interference.<\/p>\n<p>Two dipole (half-wave) antennas are included in the kit:<\/p>\n<ul>\n<li>Telescopic 46-198 cm\n<ul>\n<li>Ranges from <strong>75 MHz to 325 MHz<\/strong>.<\/li>\n<li>Covers most of the VHF Band:\n<ul>\n<li>FM Broadcast<\/li>\n<li>Aviation<\/li>\n<li>Marine<\/li>\n<li>NOAA Weather Radio<\/li>\n<li>Military Aviation<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>Telescopic 14-30 cm\n<ul>\n<li>Ranges from <strong>500 MHz to 1 GHz<\/strong>.<\/li>\n<li>Covers part of the UHF Band:\n<ul>\n<li>TV Channels<\/li>\n<li>Radio astronomy<\/li>\n<li>Mobile broadband<\/li>\n<li>ISM (e.g. 433\/915 MHz remote controllers\/RFIDs)<\/li>\n<li>Industrial (e.g. SCADA)<\/li>\n<li>Pagers<\/li>\n<li>Aeronautical radionavigation<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Antenna quality directly determines reception quality for the entire circuit.<\/p>\n<p>The best approach is to choose an antenna that precisely matches the target signal from the start. Building your own antennas is also worth considering.<\/p>\n<p>As an example, see the block diagram of a dual-conversion heterodyne receiver:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4545\" src=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/12\/Screenshot-from-2025-01-05-10-46-11.png\" alt=\"\" width=\"1032\" height=\"162\" srcset=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/12\/Screenshot-from-2025-01-05-10-46-11.png 1032w, https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/12\/Screenshot-from-2025-01-05-10-46-11-300x47.png 300w, https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/12\/Screenshot-from-2025-01-05-10-46-11-1024x161.png 1024w, https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2024\/12\/Screenshot-from-2025-01-05-10-46-11-768x121.png 768w\" sizes=\"auto, (max-width: 1032px) 100vw, 1032px\" \/><\/p>\n<ul>\n<li>Antenna\n<ul>\n<li>Captures raw incoming RF signals. Must be sized for the target frequency.<\/li>\n<\/ul>\n<\/li>\n<li>BPF1\n<ul>\n<li>A Band-Pass Filter that selects a specific frequency band (e.g. AM Band, FM Band).<\/li>\n<\/ul>\n<\/li>\n<li>LNA\n<ul>\n<li>Amplifies weak signals while introducing minimal noise, ensuring sufficient signal strength for further processing.<\/li>\n<\/ul>\n<\/li>\n<li>BPF2\n<ul>\n<li>Removes unwanted image frequencies to prevent interference during mixing.<\/li>\n<\/ul>\n<\/li>\n<li>First Mixer\n<ul>\n<li>Mixes the signal with a local oscillator signal to produce a first intermediate frequency (IF1).<\/li>\n<\/ul>\n<\/li>\n<li>BPF3\n<ul>\n<li>Filters the IF1 signal to select the desired channel (e.g. a radio station), reducing interference from adjacent signals.<\/li>\n<\/ul>\n<\/li>\n<li>Second Mixer\n<ul>\n<li>Mixes the filtered IF1 signal with a second local oscillator signal, converting it to a lower second IF (IF2) or baseband.<\/li>\n<\/ul>\n<\/li>\n<li>BPF4\n<ul>\n<li>Filters the final IF2 signal so that only the desired channel passes through for a cleaner output.<\/li>\n<\/ul>\n<\/li>\n<li>Output\n<ul>\n<li>The final signal, ready to be demodulated to extract audio or data.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<hr \/>\n<p><strong>MOST POPULAR ANTENNA TYPES<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4534\" src=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2025\/12\/Screenshot-from-2025-01-02-21-31-29.png\" alt=\"\" width=\"158\" height=\"103\" \/><\/p>\n<p>A monopole antenna is a half-dipole vertical rod. The most common type is a quarter-wavelength tall, the minimum height for self-resonance.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4533\" src=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2025\/12\/Screenshot-from-2025-01-02-21-31-23.png\" alt=\"\" width=\"80\" height=\"172\" \/><\/p>\n<p>A whip antenna is used on mobile and portable radios in the VHF and UHF bands, such as FM radio.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4536\" src=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2025\/12\/Screenshot-from-2025-01-02-21-37-07.png\" alt=\"\" width=\"76\" height=\"147\" \/><\/p>\n<p>A normal-mode <strong>helix<\/strong> (aka &#8220;rubber ducky&#8221;) is the most common antenna for portable two-way radios due to its small size.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-4535\" src=\"https:\/\/dft.wiki\/wp-content\/uploads\/sites\/15\/2025\/12\/Screenshot-from-2025-01-02-21-31-37.png\" alt=\"\" width=\"135\" height=\"159\" \/><\/p>\n<p>Full-wave loop antennas have the highest radiation resistance, and therefore the highest efficiency of all antenna types.<\/p>\n<hr \/>\n<p><strong>WAVELENGTH CALCULATION FROM FREQUENCY<\/strong><\/p>\n<p><input id=\"freq\" type=\"number\" placeholder=\"0\" \/> Hz<\/p>\n<p>Full Wavelength: <span id=\"wave\">&#8211;<\/span> m<br \/>\n1\/2 Wavelength: <span id=\"halfwave\">&#8211;<\/span> m<br \/>\n1\/4 Wavelength: <span id=\"quarterwave\">&#8211;<\/span> m<\/p>\n<p><script>\nconst c = 299792458;\ndocument.getElementById('freq').oninput = function() {\n  const f = this.value;\n  document.getElementById('wave').textContent = f > 0 ? c \/ f : '-';\n  document.getElementById('halfwave').textContent = f > 0 ? c \/ ( f * 2 ) : '-';\n  document.getElementById('quarterwave').textContent = f > 0 ? c \/ ( f * 4 ) : '-';\n};\n<\/script><\/p>\n<p>A half wavelength is a common rule of thumb for the length of a simple antenna to achieve optimal reception.<\/p>\n<hr \/>\n<p><strong>FREQUENCY CALCULATION FROM ANTENNA LENGTH<\/strong><\/p>\n<p><input id=\"meters\" type=\"number\" placeholder=\"0\" \/> m<\/p>\n<p>Frequency: <span id=\"frequency\">&#8211;<\/span> Hz<br \/>\nFrequency if 1\/2 wavelength: <span id=\"haltfrequency\">&#8211;<\/span> Hz<br \/>\nFrequency if 1\/4 wavelength: <span id=\"quarterfrequency\">&#8211;<\/span> Hz<\/p>\n<p><script>\ndocument.getElementById('meters').oninput = function() {\n  const m = this.value;\n  document.getElementById('frequency').textContent = m > 0 ? 299792458 \/ m : '-';\n  document.getElementById('haltfrequency').textContent = m > 0 ? ( 299792458 \/ m ) \/ 2 : '-';\n  document.getElementById('quarterfrequency').textContent = m > 0 ? ( 299792458 \/ m ) \/ 4 : '-';\n};\n<\/script><\/p>\n<hr \/>\n<p><strong>SEE ALSO<\/strong><\/p>\n<p>SDR Tips and Tricks [<a href=\"https:\/\/dft.wiki\/?p=4616\">Link<\/a>]<\/p>\n<p>Linux Tools for SDR [<a href=\"https:\/\/dft.wiki\/?p=4618\">Link<\/a>]<\/p>\n","protected":false},"excerpt":{"rendered":"<p>INDEX Briefing Spectrum Antennas and Filters Antenna Types Wavelength Calculator Frequency Calculator BRIEFING Software-defined radio [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-3898","post","type-post","status-publish","format-standard","hentry","category-software-defined-radio"],"_links":{"self":[{"href":"https:\/\/dft.wiki\/index.php?rest_route=\/wp\/v2\/posts\/3898","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dft.wiki\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dft.wiki\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dft.wiki\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dft.wiki\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3898"}],"version-history":[{"count":76,"href":"https:\/\/dft.wiki\/index.php?rest_route=\/wp\/v2\/posts\/3898\/revisions"}],"predecessor-version":[{"id":5619,"href":"https:\/\/dft.wiki\/index.php?rest_route=\/wp\/v2\/posts\/3898\/revisions\/5619"}],"wp:attachment":[{"href":"https:\/\/dft.wiki\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3898"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dft.wiki\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3898"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dft.wiki\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3898"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}