Can you hear the difference? New dual-mode AM/FM CB radios

user-gravatar Headshot
Updated Mar 23, 2023

For this week's Overdrive Radio podcast, Mark Karnes tells the story behind the Cobra company's petition to the Federal Communications Commission some years back to allow the use of FM rather than just standard AM in CB Radios. With the petition granted in 2021, Cobra is now out with AM/FM dual-mode versions of all of its most-commonly-used models, joining some other makers, too

Karnes, a vice president with Cedar Electronics, Cobra's parent company, notes the transition from AM-only radios to dual modes won't happen overnight. When more FM-capable radios are in play, though, he said, users will find better voice clarity over the air when used in FM mode on both ends.

Howes logoOverdrive Radio sponsor Howes is offering a prize pack including its Lifeline fuel treatment and Howes Multipurpose penetrating oil to those who send me an an email or leave a voicemail on the podcast message line. Leave your name and address and we'll get it to your doorstep: 615-852-8530.Hear a measure of that improved clarity here, as we recorded transmissions between two dual-mode versions of Cobra's 19 Mini radio, one in a moving vehicle and one in a stationary vehicle. But for dialing up Channel 15, otherwise quiet the night of the test, and slight adjustments to squelch on both units, each radio remained at standard out-of-the-box settings. Drop into a little bit of the squawk between the Ghostwriter (that'd be me) and T-Bone (a trusty assistant) in today's podcast, and get a feel for the principle difference in AM and FM modes -- voice clarity when you're nearing the edges of range, or in situations with the interference that can sometimes plagues AM transmission: 

[Related: The CB's historic role in trucking culture


Todd Dills: Should be good on the level. Hey, when this thing starts squawking, look over here and see if this light, if there's a light right here that's going up, it's too loud, and just tell me.

T-Bone: Okay. Yeah.

Todd Dills: And remember when I tell you, "Switch to FM," that button right there.

T-Bone: Yeah

Ghostwriter: T-Bone you got your ears on?

Todd Dills: So what you heard there at the top was one Overdrive editor, namely me, trying to explain to his daughter the mechanics of a little project that will be just a small part of today's edition of Overdrive Radio for Friday, March 3, 2023, where we'll be comparing CB transmissions with two of the new both AM and FM capable radios. Following the company's petition to the Federal Communications Commission to allow use of FMN radios in the US, Cobra Electronics introduced its first line of dual mode radios just this year, and sent us two identical 19 mini AM/FM models to get a real feel for the principal difference in modes, sound quality, and clarity nearing the edges of range or in situations with plenty interference. I'm Todd Dills and for this edition of the podcast, you can know me by the handle Mr. Mike Mustang Crawford once upon a time bestowed upon me. That would be Ghost Writer. W-R-I-T-E-R.

Ghost Writer: I do hope you enjoyed your first experience of CB radio.

Todd Dills: My capable hand on the other end of the line. Well since her name like mine begins with a T...

Ghost Writer: Well T-Bone, I appreciate you helping me out on this little here test.

Todd Dills: I set her up with my audio recorder and one of the 19 Mini AM/FM units in a vehicle at the house and then with my own unit and a different vehicle ran the same route up to 3/8 to about half a mile out from the starting point at the farthest distance. We're in a Nashville neighborhood here in Tennessee with plenty of opportunity for interference all around, including from my neighbor who happens to be a ham operator. He was certainly more help than harm here though. He solved one problem I had in running the test. I only had a single very simple and well aged magnetic roof mount antenna. When I asked him if he had something we might borrow to get the second device going, he said, "Well no, but give me an hour, I'll build you one." And so he did and we were off at the races.

Ghost Writer: I still got you there. T-Bone?

Todd Dills: We'll hear more from the Ghost Writer's little run throughout, but also directly from Mark Karnes, vice president with Cedar Electronics, parent company of the Cobra brand, and who's been with Cobra going way back.

Mark Karnes: Yeah, so I have been at executive in various roles. I started off with Cobra Electronics before it was merged and we became Cedar Electronics. But in that, the various roles and titles, I've always been into the product marketing aspect of the company and today that, I'm an executive, I'm a vice president of product marketing and business development. And the business development is sort of a means to an end. If we look at something and we feel that we need sort of the development, whether it's market development, business development, we need to work on standards with various associations. My role is to assist in those areas and lead those areas when necessary. And part of that is I'm a member of the vehicle technology division for the Consumer Technology Association. I sit on the Marine Electronics Board, I'm with the SEMA board, and I also play different roles with some of the trucking and transportation industry councils,

And in that you get a lot of exposure to the various elements of need from both the carrier side of the coin to the driver side of the coin.

Todd Dills: When we pick up with Karnes after a break, he emphasizes that a lot of what led the company down the road to petitioning the FCC to add allowance for FM capabilities to the CB radio came from. Well, what else but the needs and concerns with the performance of the end user? Perhaps most important among those CB users, of course, professional truck owners and operators.

Speaker 4: When you have a diesel emergency, you don't have time to wait around for 911. Instead call your lifeline. Howes Diesel Lifeline. The only emergency rescue product to re-liquify gelled fuel and de-ice frozen fuel filters without the use of harmful alcohol. Always safe to use, you can pour it directly into your fuel filters without wasting time mixing it with additional diesel fuel. So this winter, if you find yourself stuck in a bind, skip the tow, get yourself back on the road fast with Howes Diesel Lifeline. For more information, visit

Todd Dills: Here's Mark Karnes speaking to the long importance, the needs of the end user and his company's long ongoing product development.

Mark Karnes: And for us in Cobra, especially when you look at the long history in CB radios, we really look at that as not only a tool for conducting business by truckers, but it's really, it could be the means of social media for them. It's how they communicate during their long, lonely drives cross country, and they've really turned the CV radio into the first electronic chat room ever invented. And you have to really respect that aside from the information that they get to conduct their business, that this is something that really keeps them, keeps them alert, keeps them informed, and just keeps that level of social isolation at a minimum.

Todd Dills: The dynamic Karnes is describing as no big secret for listeners here of course. Around the time of the rise of so-called social media, 10 to 15 years ago, many of the owner operators I knew took to calling the CB and the communication and more enabled by it the quote, "Original social media" in fact. Track back through some of our older Overdrive radio episodes and you'll find one all about that notion, and the history of owner-operator, Mike Mustang Crawford within it. The same Mustang I mentioned up top, of course. I'll post the link to that episode in the show notes if you go searching for it, otherwise the title's having a little fun with Mustang's former CB handles, "How the Lucky Turkey became the Maverick, became the Mustang", of course. The upshot is that the humble CB played a huge role in trucker culture and evolution through the years.

Mark Karnes: And you have to kind of take that pretty seriously. So when you look at something that is an age-old technology like CB radios... And I'm talking to people, they're always asking, "Gosh, I didn't even know CB radios were still made." And I go, "Yeah, it's like next time as you're driving down the interstate highway, look up at that truck you're passing and if you see some antennas, that's his CB radio and that's how they talk truck to truck." And they're like, "Oh, I didn't know that."

So to get to the background of why FM, CB rests on AM, and an AM and then the 25 megahertz band that CB operates in, it was really put together in the late fifties and early sixties. And COBRA has made an effort over a number of years to try to deal with situations to help improve it.

But this comes from (a) we're going to go from 19 channels to 40. Well why did we need to do that? Well, the traffic increased so much across the use cases that the people were stepping all over each other. There's various technologies that you can deal with AM and why do you put them into play? Because people have a tough time understanding each other. And there are various ways that people go about trying to improve its range, but the biggest issue that they fight with is not the range, it's so much, it's the quality of sound. "How can I actually hear what's going on?" And you know, can be on there and listen at given times going down the road and yeah, it's pretty hard to understand some people, accents aside. And when we looked at the number one issue that we thought we needed to tackle was "How do we bring higher fidelity into the use of a CB radio?"

And we all know back in the days when it was AM radio for entertainment and FM came into play, what transformed in terms of the quality of the music experience. And we know that we had to solicit to the FCC before they made really any hard decisions on spectrum, that we're not asking the FCC for more spectrum. What we're asking the FCC to do is allow us to change modulation so that we have the capability when range isn't the only thing you need and you want sound quality, that the user of this can go to that experience. And we work with the FCC to explain how this isn't going to interfere with other use cases, ham radio operators, a number of things. But in general, what we were appealing to is the fact that we could use the band that has been associated with it for decades and we can improve the experience and by doing so, it will help drivers communicate to each other.

And the FCC does look at this and say, above all, we're here to make sure that the people who use this can use it properly and use it to their advantage. So while it took a little bit of technical convincing and the fact that we wanted them to adopt a dual mode approach so that nobody is isolated no matter what the transition experience will be, and laid all that out and how we would accomplish that, really gave the FCC the confidence that they could implement something like this and it would be a benefit to the radio user, and it wouldn't isolate or obsolete somebody's approach to using their CB radio.

Todd Dills: I just want to make sure I'm hearing you right there. In terms of that dual mode approach, so what you're saying is, the FCC changed was the ability to have AM and FM capability in a single unit, but not to just produce FM only CB radios is the idea.

Mark Karnes: Yes. We did not want them to just say it's all, "Oh, we're going to go to FM now." We're like, "Whoa, whoa, whoa, whoa, whoa." We got millions of people out there who have AM CBs and they may choose to use it. It may be the better method when they're out on an open desert road of being able to communicate to each other because they need the additional distance. What we wanted to do was say, "Look, we want dual mode so that when we start off with this and we enter into it with let's say one of our most popular units like the 29 LTD, we can put dual mode and somebody can buy this and when there is a good install base of FM users, they're going to start to really enjoy being able to travel down the same interstate highways that they're used to, and then now they can hear every word the individual that they're trying to reach is saying."

And if their buddy still has an AM radio and he wants to talk and he hasn't made a change yet or hasn't decided that it's time to move over, he can still communicate on the AM band user as well.

So the dual mode really helps the whole transition period. And CB users are not prone to changing their products very quickly.

Typically, they're going to do so when it breaks or there's a reason to make a change. And that could happen in a normal sequence of five years, let's say. And we do make considerations that our products are built so heavy duty to last that long, but we are implementing a technological benefit that will be immediately available to those people who own that product. And when there are enough of those people out there who own those products, it will become kind of the commonplace use.

Todd Dills: It might be difficult to find an FM user out there right now, right?

Mark Karnes: Today, yes. At the end of the year you'll start to be able to go, "Oh, he's on FM." And by this time next year, and I think within the 24 to 36 month traditional adoption cycle, you'll go from very little on a road, to they'll be high concentrations of it, till it'll be pervasive

Todd Dills: If Karnes is right, and the AM/FM dual mode units get more and more common, you can learn to recognize when an operator is on FM and you're on AM. Here's what it sounds like to receive an FM CB transmission on a CB communicating on AM courtesy of the Ghost Writer and T-Bone as it were.

Ghost Writer: Can you hear me now?

Todd Dills: We were but a few car lengths away from each other at that point, you guys just should know. And then when the receiver switched over to FM and both CBs were in FM mode, this is what it sounded like.

Ghost Writer: Got your ears on? So how's that sound? Is that noticeably different?

Mark Karnes: We wanted to make an investment in not that FM is at the high end of the spectrum, but dual mode is going to be implemented in every one of our most popular sellers first. So if you go to MATS and you look at the display in our booth, you see the entire classic series in front of you with dual mode. And that means we're going to commit to the highest volume runners, in the highest level of replacement because it has the longest install base first, so that we can help facilitate the transition in the most expeditious way. It's not to say we're not going to have some cool stuff that comes in there and if you happen to be at MATS, I'd like to have you come by our booth. I'll show you something really exciting. For now the commitment really is that our 29 classic series has its best movers with the dual mode already implemented right now.

Todd Dills: Karnes elaborated a little bit on just what that exciting product news at MATS would be, but yes, just a little.

Mark Karnes: Yes, we were committed to making sure that our most popular runners at the lowest parts of our price point were going to be immediately available to make the transition. But we also took the opportunity to make sure some state-of-the-art product, when it arrives, is really encompassing everything that we envision it to be.

Going to see that with another one of our partners that will answer the second most asked question which I'll be happy to demonstrate to you when you come by the booth.

Todd Dills: Any chance I can get you to tell me what that second most asked question is?

Mark Karnes: I'm still on embargo so...

They would shoot me if I did that.

Todd Dills: Now it hasn't been a lot of time since Cobra's had this line of dual mode CBs available, but I know there have been some other manufacturers that have had them out since I think last year, maybe even a little bit earlier. You could correct me if I'm wrong on that, but are you seeing a lot of truckers take these up? Is just one thing I was curious about.

Mark Karnes: The adoption right now is really small now. It was President that kind of co-signed onto the petition with FCC.

They're a European base company.

FM has been in use in Europe for some time. So it was to their advantage to have it switch over to FM so they don't have to make entirely different products for different regions. But they're pretty small in the marketplace. So not to brag, but we have a considerable section of the market, and you'll go to local truck stop retailer without seeing four or five units on display to be sold right there and installed while you wait on your rest period. Some of the other smaller brands aren't that fortunate. So the advantage here will be that availability at the point where the truck driver can make his decision and when he's on rest period. That's what's going to make the difference with acceleration of the adoption rate. And our partners, our retail partners, are queuing up right now so that as we all go into the springtime, you will see dual mode systems available from everybody.

Todd Dills: What is the range difference on any given unit between just the AM and FM modes on the same channel, same antenna, everything else? Is that something that's quantifiable? Is it significant?

Mark Karnes: Well, it's a great question. So technically the transceiver, that is the final part of this, is the same. So the four watts apply to AM, four watts apply to FM. Think of it in aspect of it's the quality of the quantity. I can hear really, really good till I can't. And with AM sometimes even when the person is just a half mile away, you can barely hear over the static and things that are out there. And you're tweaking and your squelch and all your noise blinkers and you pick him in. FM, it's kind of like an automatic thing. It sounds great and then it fades away. I don't have [inaudible 00:18:52].

What's the difference in range? I'm going to tell you that you'll not notice a range difference in high population areas. What you're most likely to notice is that when you're in an area like an open desert or an open plains area where you don't have the background electronic noise going on, you can make out that AM signal a little bit longer than you could FM, because FM will not tolerate the noise in the background. It just says, "It's not a signal I can make good, you won't get it." There's no differences in antennas because the final amplifier section is the same. It's the same frequencies. It's really going to be the fact that your FM transmission is less pervious to noise. So if there's another broadcast antenna, like your buddy, if he's a ham operator, he's queued up with a fair amount of wattage, he can overload an AM front end really quickly and it's in it's garbled, where the FM is not going to be susceptible as susceptible to that situation.

These are things that you'll notice. It's like if you, you're in Nashville, the neon signs and all the other things that are on Broadway, they have a particular frequency that they hum at that AM devices don't like.

If you are transmitting and receiving both on FM in that same area, you're like, "Oh, no problem."

Todd Dills: And when T-Bone and the Ghost Writer tested the modes, we heard some of this a bit, particularly at the farthest points when the traditional AM communication got particularly staticky.

Ghost Writer: Can you catch me now?

T-Bone: What?

Ghost Writer: You still got me?

T-Bone: Yeah, there's a little bit more static in the background now, but I can still hear you.

Ghost Writer: Right. That's what happens when you get the distance between you. So now I'm at, I'm actually, I'm actually going to cut this short and go down Franklin, and I'm going to head back and when I get back we're going to switch over to FM and try the same route and see how that sounds.

Todd Dills: And now from that same distance in place with both units in FM mode.

Ghost Writer: I'm going down 14th. I'm getting pretty close to the stop sign at Franklin. How’s it sounding?

T-Bone: I can still definitely hear your voice well. I think there's like less, it's less muffled than it was last time.

Ghost Writer: Turning on Franklin now, headed down Franklin, and this is on the FM as opposed to the AM. I'm headed down Franklin and getting ready to turn. I'm back onto 16th, coming back towards...

Mark Karnes: That's kind of the experience that you'll receive. It'll be like breathing new life into an old radio.

Todd Dills: Here's a big thanks to Mark Karnes for his time. You can find much more about the new AM/FM dual mode CBs that Cobras got out now via My colleague Tom Quimby also recently updated a 2021 story with detail on the variety of manufacturers now offering AM/FM units, including Cobra of course. Find a link to that story in a post that houses this podcast for Friday, March 3rd, 2023 at I'll drop it in the show notes too of the podcast wherever you're listening, where you can also give us a rating or review if you're enjoying these episodes. Apple and Google Podcasts, Spotify, Stitcher, SoundCloud, and so many others. For any feedback from me, dial (615) 852-8530. Leave a message there on a podcast line.

Ghost Writer: This is the Ghost Writer and we will be over and out.

All right, T-Bone, do you know how to turn that car off?

The Business Manual for Owner-Operators
Overdrive editors and ATBS present the industry’s best manual for prospective and committed owner-operators. You’ll find exceptional depth on many issues in the Partners in Business book, updated annually.
Partners in Business Issue Cover