# CB and Shortwave

#### biferi

Joined Apr 14, 2017
342

If CB has 40 Channels how many Channels does Shortwave have?

#### Papabravo

Joined Feb 24, 2006
19,564

If CB has 40 Channels how many Channels does Shortwave have?
They are entirely different things. CB channels are narrow band short range voice channels in the US. I'm not sure they even exist in the rest of the world. The shortwave broadcast bands are setup by international agreements and are designed for wideband broadcast channels. Since shortwave broadcasts can propagate around the globe when conditions are right stations must agree not to broadcast on each other's frequency allocations. since these shortwave stations also broadcast music, the channels need to be wider than voice only channels.

#### DickCappels

Joined Aug 21, 2008
9,505
Essentially infinite - frequencies may be assigned for some services and not for other Shortwave services.

#### biferi

Joined Apr 14, 2017
342
I think I understand now?

Shortwave goes all over and when somebody is no longer Transmitting another Person can use the same FREQ am I Right?

So they do not Break Up the FREQ. into CH. Right?

#### DickCappels

Joined Aug 21, 2008
9,505
It depends. International shortwave radio stations don't share their frequencies easily, but in the amateur radio bands it is like what you described it - people come onto a frequency, use it then it becomes available for another conversation (not counting special cases).

Right. There are specific frequencies reserved for special uses, but the concept of "channels" does not work well over most of the shortwave bands and frequencies, as far as I know, are not assigned that way.

#### biferi

Joined Apr 14, 2017
342
Ok now I think I am getting the hange of how it works.

Now CB has 40 CH. and it is an 11 Meter Band.

Am I Right this is telling me that all of the FREQ. in the CB Band are 11 Meters Long?

So the Start of one FREQ to the End of that same FREQ. will be 11 Meters Long.

Am I Right?

#### BobTPH

Joined Jun 5, 2013
6,065
11 m is the approximate wavelength of all the frequencies in the band.

#### Papabravo

Joined Feb 24, 2006
19,564
Ok now I think I am getting the hange of how it works.

Now CB has 40 CH. and it is an 11 Meter Band.

Am I Right this is telling me that all of the FREQ. in the CB Band are 11 Meters Long?

So the Start of one FREQ to the End of that same FREQ. will be 11 Meters Long.

Am I Right?
The relationship between frequency and wavelength is that the product of the two is always equal to the speed of light.

$$c=f \times \lambda$$
$$c\approx3\times 10^{8}\text{ meters/sec}$$
$$f=\text{ frequency in Hz.}$$
$$\lambda=\text{ wavelength in meters}$$

For example, the 49m shortwave band is from 5.9 to 6.2 MHz. So,

$$300/5.9\;=\;50.85\text{ meters}$$
$$300/6.2\;=\;48.39\text{ meters}$$

The "wavelength" they use for the whole band can be thought of as a kind of average although it is neither the arithmetic mean nor the geometric mean.

Last edited:

#### SamR

Joined Mar 19, 2019
4,484
CB is primarily AM on 40 "channels" in the ~28MHz or 11M band. Limited by law in the US to 4W but often using illegal linear amplifiers of much higher wattage. It also supports single sideband which never really caught on as a viable transmission mode for CB. There is also an amateur radio 10M band which, when the band is open, I've used @ 100W for contacts from my home in Coastal Georgia USA to operators in Europe and Northern Africa along with places such as the Canary Islands off of the western coast of Africa and other Atlantic Ocean islands.

#### Ya’akov

Joined Jan 27, 2019
6,853
International agreement and practical considerations determine the frequencies shortwave broadcasters will use. To avoid interference, broadcasters stick to what are essentially channels, with the center frequencies determined by the limits of the relievers used by listeners.

The difference between the numbered channels of US Citizen’s Band radio and the functional equivalent for shortwave is that there are no numbered channels for shortwave. The channels are specified by their center frequencies. Non-broadcast stations are more free to use odd frequencies, but because of similar reasons to broadcasters, they will generally stick to conventional ones.

#### Papabravo

Joined Feb 24, 2006
19,564
International agreement and practical considerations determine the frequencies shortwave broadcasters will use. To avoid interference, broadcasters stick to what are essentially channels, with the center frequencies determined by the limits of the relievers used by listeners.

The difference between the numbered channels of US Citizen’s Band radio and the functional equivalent for shortwave is that there are no numbered channels for shortwave. The channels are specified by their center frequencies. Non-broadcast stations are more free to use odd frequencies, but because of similar reasons to broadcasters, they will generally stick to conventional ones.
In some cases of extremely narrow band data modes like PSK-31 and FT8 it is possible for many transmitters to be on the same carrier frequency but not interfere with each other because of the modulation technique.

#### Ya’akov

Joined Jan 27, 2019
6,853
In some cases of extremely narrow band data modes like PSK-31 and FT8 it is possible for many transmitters to be on the same carrier frequency but not interfere with each other because of the modulation technique.
Yes, digital modes that can pull data out of what sounds to the ear like nothing but noise are amazing and change some of the rules.

#### biferi

Joined Apr 14, 2017
342
I am looking at a CB Radio to talk to Truckers and People.

How Far will they go in Miles?

#### SamR

Joined Mar 19, 2019
4,484
Depends on several things such as time of day (signal propagation), height of antenna (higher is better), gain of antenna (if any), antenna tuning (what is the SWR), and signal quality (is the radio properly aligned). So anything from a few miles to, well, I've talked to people over 1000 miles away when band conditions were just right. Nighttime gets quieter and distance gets further (once again signal propagation) from a few miles to making contacts in the next few counties at best. Then there are beam antennas... Lots of truckers have abandoned CB or only use it as a secondary mode and are using illegal 10M Ham Radio mobile rigs.

#### WBahn

Joined Mar 31, 2012
27,855
I am looking at a CB Radio to talk to Truckers and People.

How Far will they go in Miles?
It depends on LOTS of variables. A common rule of thumb back in the day when CB and handheld walkie-talkies (most of which used Channel 14) were real popular was one mile per watt under "typical" conditions. Even as a kid I was real skeptical about how accurate that could possibly be and I have no idea upon what it was based -- could well have been just some marketing guy's brainchild.

#### Externet

Joined Nov 29, 2005
1,957
To make it more convoluted, yes, CB is shortwave, between 3 and 30 MHz, now called HF or 'high frequency', and used with different modulations as AM, FM, CW, SSB,. DSB, VSB, RTTY and several more, and channelized or not depending on the service.

#### Janis59

Joined Aug 21, 2017
1,523
RE:""If CB has 40 Channels how many Channels does Shortwave have?""
11 m =300/11=29 000 kHz minus 160 m = 300/160=2 MHz thus dF=27 000 kHz divide to channel width 10 kHz = 2700 channels.