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.
Notify of

Inline Feedbacks
View all comments

no its 36 feet aprox for ;full wave antenna for 27mhz range anyway but we know the 102 inch whip is 1/4 wave ‘just sit 4 n top reach othr it would 102 inches x 4 ‘TO BE BE A FULL WAVE ANTENNA ‘DONT THINK 43 WOULD WORK ..too talll


i was recently in the US doing a little road trip, CB was handy and even in the Nevada desert there were voices on AM CB occasionally… one Guy told me there were a few people ‘finding’ CB again or coming back after a long time absent.. the reasons given were varied, and i was very interested to note some people noted the fact that it’s non-centralised, free, non-controlled, anarchic, ‘Big Brother’ snoop-free, it doesn’t need expensive and complicated computer gear, data plans, ISPs, cell-bases, Adverts, security issues, spyware, spam, junk or need you to stare into a screen..
I started CB just after i got my first 2m HT back at school in the late 70s, CB was fashionable and 2m wasn’t – and there were lots of Girls on CB too… a big plus point to a teenage guy – even with a Ham license.. i spent more time on CB naturally. Today i don’t use CB – though the FCC AM/SSB 40ch is now legal here in the UK, poor band conditions, PLT noise and easy gratification of Internet still seem to have made CB dead in the UK here.. Yes there are pockets of use, but CB is as dead as any mode on 2m or 70cms here – and the only activity we’ve had consistently here is our local 28.495 net.. but even that rarely produces much more than 3 or 4 regulars.
Here in the UK, apart from my 10m SSB fun, a good part of my hobby involves listening to 27.025 am (the Superbowl channel) as it can quite unexpectedly open up for either 5 minutes or a few hours for no apparent reason 🙂 – it’s a little like beacon watching.. and even in solar minimum this can, and does happen, and so a RTL SDR can be pressed into service for this purpose if you fancy a change, or want to run a feeder into the bedroom and monitor at night and can’t be bothered seeing radio hardware up.. i use GQRX on the Mac and the RTL dongle – and the NB on the SDR gets rid of much of the hateful PLT i have to suffer with on 11m here.
25.555 (usb) is now the ‘de facto’ SSB calling frequency in much of the world, and 27.385 LSB sees to be the North American SSB CB frequency, It’s a pity legal UK SSB/AM in the UK doesn’t include 27.555 though, and there’s not enough SSB CB use in the UK for them to get together and (logically) create an ‘official’ UK SSB calling frequency.. like Portugal have – 27.345 LSB (if you like echo on SSB- yuk).
As N0BGS says above UK AM/SSB/FM is now legal in the UK on the 40 FCC channels.. although, the strange American channel jumps and hops seem to not be present in the Eu spec of band.. which could be cause for confusion if CH numbers are used in some circumstances. I wish CB would take off again. I’m sick of communicating via computers and the whole complicated infrastructure it demands..

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.


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.

Staci Gullickson

Great analysis – Just to add my thoughts , others have been needing a FCC Form 740 , my business encountered a template version here FCC Form 740.


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 .


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


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.


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.


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

Or a 102 inch whip…


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.”


Sorry, I typoed that. Correct range is 26.965 – 27.405