Question about the AM to FM migration of CB radio.

[whirled-traveller]

I have a question about this proposed migration of CB going from AM to FM

• If someone transmits in FM mode, will my old CB radio be able to pick up the signal, decode it, and play the comms on the speaker since my radio is AM? Or would both radios have to be in FM mode? If the answer is no, how would someone with an AM radio know that someone is on the channel transmitting and receiving in FM?

I am wondering about this as I am currently back to using my super old Uniden Pro510XL (as my main radio died). I have been thinking about my replacement and now with AM and FM, I am waiting for the market to settle with new AM / FM models (Cobra, Uniden preferred) or before buying another radio.

 

[prcguy]

There is no migration to FM, its just another optional mode like AM or SSB. I expect some people to use it but with AM and SSB being the dominant mode for the foreseeable future. If you listen to an FM signal on an AM receiver right on frequency it will be very distorted and you may make out some words. If you use a clarifier and tune off several to about 5KHz you can tune it in pretty good and it doesn't sound bad. Since FM on CB will be narrow band the audio level will be a little low receiving off frequency on an AM receiver.

 

[mmckenna]

I have a question about this proposed migration of CB going from AM to FM

It's not proposed, it already happened.
It's not a migration, it simply allowed users to utilize AM, SSB or FM.

• If someone transmits in FM mode, will my old CB radio be able to pick up the signal, decode it, and play the comms on the speaker since my radio is AM? Or would both radios have to be in FM mode? If the answer is no, how would someone with an AM radio know that someone is on the channel transmitting and receiving in FM?

No. If you have an AM radio, you are only going to be able to communicate with others using AM.

I am wondering about this as I am currently back to using my super old Uniden Pro510XL (as my main radio died). I have been thinking about my replacement and now with AM and FM, I am waiting for the market to settle with new AM / FM models (Cobra, Uniden preferred) or before buying another radio.

I'd wait.

Keep in mind that most of the rest of the world has allowed FM on CB for a long time. Most of the large CB manufacturers already have FM capable radios, they just were not approved for use in the USA.
The standard chosen by the FCC matches what other countries are using, so bringing these FM capable radios in from other markets is fairly easy. The radios need to be submitted for type acceptance testing. President has already done that and has some radios on the US markets.
Not sure what the other manufacturers are doing, I suspect they will slowly follow.

FM isn't going to take over any time soon (or ever). Most legal CB's out there in the USA are AM only or AM/SSB. It's going to take quite a while for FM to make its way into common usage. Early on, it's going to be the "early adopters", usually that's the serious hobbyists that want the new toys. I think it's going to take a long time for FM capable CB radios to really become popular. There's better options out there.

 

[spongella]

Good question and excellent answers.

I've been listening on 11 meters for the past month and it's been open almost every day. The only FM ops heard were DX stations and none from the US. It's interesting how far FM can travel when the band is open as I've heard ops with British accents carrying on conversations. Also heard French and German ops using FM. In the US, AM and SSB still are the dominant modes from what I've heard.

Interestingly, SSTV signals were heard on 27.700 megs occasionally. That's above our (US) CB band though.

 

[Ishmole]

Good question and excellent answers.

I've been listening on 11 meters for the past month and it's been open almost every day. The only FM ops heard were DX stations and none from the US. It's interesting how far FM can travel when the band is open as I've heard ops with British accents carrying on conversations. Also heard French and German ops using FM. In the US, AM and SSB still are the dominant modes from what I've heard.

Interestingly, SSTV signals were heard on 27.700 megs occasionally. That's above our (US) CB band though.

FM can be amazing. During the last cycle the band was really hopping. I had numerous FM simplex contacts on 10 meters around 29 MHZ with 20 watts from NY to all over Europe.

 

[KMG54]

I can only get a few guys around here to even try FM even though they have the radios. For a guy like me with really bad hearing, FM is so clear it would be my preferred method.

 

[empireco]

FM on CB will also eliminate the interference caused to people's poorly shielded sound systems in their homes and churches that auto-rectify
the signal and it's heard over speakers unintentionally. Using FM would also stop most of the band splatter of people using illegal amps as most of them are class B or C and are meant for FM anyway.

 

[prcguy]

It may stop the voices from coming out of church PA systems but it doesn't actually eliminate interference, it can still get into PA systems. In my experience if you caused interference in AM or SSB mode, switching to FM can make the speakers thump when you key up and sometimes have a hum. RFI is RFI no matter what the modulation format is.

FM on CB will also eliminate the interference caused to people's poorly shielded sound systems in their homes and churches that auto-rectify
the signal and it's heard over speakers unintentionally. Using FM would also stop most of the band splatter of people using illegal amps as most of them are class B or C and are meant for FM anyway.