A Guide to Listening to CB Radio with an RTL-SDR Dongle

In the June edition of The Spectrum Monitor, SDR enthusiast and ham Mario Filippi N2HUN published an article titled “Your New CB ‘Good Buddy’, the SDR Dongle”. While the CB radio heyday is well and truly over, Mario discusses how an RTL-SDR dongle can be used to have some fun listening to CB without needing to go out and buy a full CB radio. If you don’t know what CB radio is, Mario explains what it is, and its rise and fall in these excerpts:

In the mid-1970’s an early form of social media was sweeping across the country known as CB (Citizens Band) radio. In those years the FCC required CB radio operators to obtain a license, easily gotten by filling out FCC form 505, paying the fee ($20 or $4 depending on what year you applied), and waiting very patiently, usually two to three months for your license to arrive by mail with your call sign.

The concept of wirelessly communicating with others without studying for a licensing exam somehow caught on and was embraced by the American public. As a result, in the mid-70’s CB sets started flying off the shelves by the millions to appease this new insatiable appetite of Americans to talk over the air with their “good buddies” (CB slang for friend). Other major factors played into the oncoming tsunami of CB’ers: gasoline was getting scarce as a result of the recent oil embargo, prices were quickly escalating at the pump, and the Interstate Highway maximum speed was lowered to 55 MPH prompting drivers with heavy feet to communicate the whereabouts of radar-enabled local police (CB slang: Smokies or Smokey Bears) or the cheapest place to fill up. In addition, traffic information such as road conditions, accidents, speed traps and the best greasy spoon location was now available to the commuting public by simply turning on the CB radio and tuning to the trucker’s Channel 19, the epicenter for the latest road-related poop.

By the late ‘70’s there were so many CB’ers congregating on the air causing non-stop channel chatter and ignoring FCC regulations (C.F.R. Part 95) that Uncle Charlie (CB slang for the FCC) eventually dropped the license requirement. The American public now ruled the airways with expanded 40 channel radios and pandemonium. Call signs were replaced by nicknames or “handles” and everyone prided themselves with their own, unique self-descriptive moniker when “ratchet-jawing” (slang for talking a lot) on their CB radio. But when the early 80’s rolled around the public’s fleeting romance with this mode of communication had dwindled markedly and only the diehards remained on the air in happy solitude.

The article goes over several points which may be useful to those who did not play around on CB back in its popular days. He explains how CB radio exists on frequencies between 26.965 MHz to 27.115 MHz and how you should use an appropriate (large) CB antenna, such as an 43 foot S9 vertical antenna. He also notes how CB radio conditions can be affected by ionospheric conditions, and how on a good day (CB is usually open during the day as opposed to the night for the lower frequencies) you can actually receive CB radio from all over the world including Europe, the Caribbean and the US. 

As the article is a part of The Spectrum Monitor magazine it is not free to read, but each monthly edition only costs $3 USD, and comes with multiple articles from other authors too, which makes it quite a good bargain read every month. You can find the June edition at http://www.thespectrummonitor.com/june2015tsm.aspx.

CB Radio coming in with an RTL-SDR and CB antenna on SDRSharp.
CB Radio coming in with an RTL-SDR and CB antenna on SDRSharp.


  1. Rodney Hodge

    I’m big into cb radio never been into ham radio but have thought about it. A fullwave antenna on the 11 meter band is 36 foot long but I have never once heard of anyone using a fullwave on the 11 meter band. Far as ground plan antennas the best I have ever used is a 5/8 called a shockwave built in alabama. I’m 37 years old and have own a lot of deffrent ground plan antennas. I have own Antron 99 imax2000 Maco v5000 jogunn pistol jogunn son of a gun jogunn hillbilly shackspear army big stick srio 2016 sirio gain master Skylab penter 10k spt500 mr.col .64 and the shockwave has been the best out of all them.

  2. Steve

    Lots of people are still using the CB radio today. When the band is open, you can hear stations pouring in from all across the country on AM channel 19 and other channels, as well as loads of stations operating lower side band on channel 38! There are also a huge number of people operating “Freeband”, above and below the official CB radio spectrum.

  3. pete

    I use to be a truck driver, and tell truth, we never had a 34 foot antenna , 19 foot antenna, or a 102 inch antenna. The most ridicules length was 48 inches for truck drivers, but most was shorter. Unless your on the moon .

  4. Warduke

    Uh I think that is a type, the size of a CB antenna is no where near 43 feet. More like 19 feet. The Antron 99 was the Best CB Antenna to have in the United states in the 80s and 90s and that was a 19 foot tuneable antenna

    • AD5NL

      Yes, what’s being suggested here is a 43 foot vertical that is used (I assume with a tuner) to cover the HF ham bands.

      Typical dipole would be on the scale of 17.5 feet; not sure if the Antron-99 is designed as a coaxial dipole (where the coax runs to the feed point inside of one of the elements) or if it is a 5/8ths wave monopole. If it is a monopole it would need a ground plane of course.

      “Best” is of course relative; a dipole is easiest to install but a 5/8ths-wave vertical should have some gain. Likewise with a J-pole or any kind of collinear vertical.

      As I noted, 102 inch whip is typically used as a quarter-wave monopole for CB, especially on trucks, and should be sufficient for most applications (and frankly *ought to* outperform the 43 foot vertical because it is resonant). Because they are cheap and plentiful (you can get the whips at hamfests for like $15), I tend to prefer them, especially for 10 meter operation. I also use 102 inch whips in lieu of the stock telescoping whip with the MFJ apartment antenna; with that tweak I am able to operate on 80 meters.

    • Michael

      Wow the Antron 99 was never the best. The super big stick was the best fiberglass stick, it was Avanti that ruled the airways in the 70’s and 80’s with the Astroplane. Moonraker and Sigma. A RadioShack 1/2 wave was better than the 99. Jeeps, cars and trucks used the 102″ whip bumper mount and body mount ball the K40 was big too for rear deck mounting. Big rigs mostly ran what would be called a fire stick today. The predator and other mega power antennas we’re rare, but very available.

  5. AD5NL

    “… and how you should use an appropriate CB antenna, such as an 43 foot S9 vertical antenna.”

    Or a 102 inch whip…

  6. N0BGS

    Legal US CB frequency range is actually 26.965 Mhz (Channel 1) to 27.205 Mhz (Channel 40). Of course, many ignore those limits and operate on frequencies considerably below and above that range aka the “lowers” and “uppers.”

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