What is the real reason for the gap between 22 and 23

[TheCBDoctor]

I posted this before but the response went to the bottom of the posts. I wanted to provide the true reason that channels 24 and 25 were placed between channel 22 and 23. I read the reason from a book written in 1968. I know if it is on the Internet it must be true but the reality is nothing beats a book written at the time when CB was coming into its heyday.

The reason there was 20 KHz gap between channels 22 and 23 was because channel 23 was used on a secondary basis for remote control. The method of transmission was a dual sideband carrier-suppressed output at 25 watts PEP. Believe it or not it was used for industrial purposes. It was used for voice as the other 22 channels, which was and remains 4 watts carrier and 12 watts PEP.

With no carrier and a dual side-band output, splatter was a possibility. This is why channel 22 and channel 23 are 30 KHz apart. Once it was realized that industry and Citizen's Band could not coincide and share the same frequency channel 23 was abandoned by Industry for remote control use, not to mention that electromagnetic disruptions, such as lightning, would interfere with the remote control. Industry was not controlling tiny model cars, but many large machines, such as, full size automobiles. Today, FM is used for remote control because electromagnetism does not interfere with FM (Frequency Modulation). Implementing digital signals made remote control more reliable on top of this as well.

Each CB channel frequency is 10 KHz wide. Five KHZ is used for voice and the other 5 KHz is split into two to provide a 2.5 KHz band-guard. For a Dual-Side band suppressed carrier at 25 watts Peak to Peak output a larger guard-band was required. Hence....20 KHZ between 22 and 23.

In 1977 when 40 channel radios were introduced channels 24 and 25 were placed in between Channels 22 and 23. Why they did not just rename the channels and put them in order made sense at the time. Twenty three channel radios and 40 channel radios had to work in conjunction otherwise anyone talking above channel 22 would not align with each other if one operator had a 23 channel radio and the other operator had a 40 channel radio.

One final point of interest: It was almost decided to make the CB Band 100 channels with a bandwidth of 5 KHz instead of keeping the channels at a 10 KHz spacing, but there were too many 23 channel radios in operation. The FCC decided on keeping the 10 KHz spacing and limit the channels to 40.

I did not get my information from the Internet. (Of course if it is on the Internet it must be true). I received the information from a book published at the time when adding channels was still a suggestion, and the use of channel 23 as a secondary purpose had just come to an end. The book was written between 1966 and 1968. The CB band, which was part of the 11 meter band was a military frequency during WWII. After the war the CB band was cut out of the spectrum and given to the Civilian population. Henceforth, "Citizen's Band."

There were 2 other classes of CB radio in the UHF band, Class "A" and Class "B." Both of these bands were eventually abandoned from non-use. UHF was expensive because tubes that operated in UHF were expensive. For some reason in Australia these two bands survived. Their HF CB band was limited to 18 channels. In Europe FM was allowed. In the USA only AM and SSB is allowed.

The Internet is a great resource; don't get me wrong, but nothing beats a book written at the time when it all was happening. The book is out of publication and is in my pile of stuff somewhere. One day I will dig it out and refresh my memory (What is left of it).

One last thing I remember when reading the book. At the time the book was written the trucking industry was required by law to have a HF CB radio installed. That was what made the CB band explode to the scene. It was in fact "back in the day" the poor man's "Cell-Phone"

Respectfully as always

Rick

The CB Doctor (Retired)

[pabxone]

My understanding of the gap between the 2 channels was due to the ITU's allocation of 27Mhz to an ISM band use.

ISM = Industrial Scientific and Medical.

We had (and probably still have) RF welders and Diathermy machine running somewhere near 27.200 - It was probably more likely 27.235 as I've not been near one for 25 years - memory fades.

27.240 was allocated as a "Bushwalkers" channel for use with low powered (Less than 1 watt) Walkie Talkies and similar low powered LMR devices here in Australia.

We also had allocation of Remote Control devices in 27Mhz - in reality they probably were actually using all the "A" channels but I think the correct allocation was 27.250 or thereabouts.

The 20khz allocation to the industrial use makes sense - RF welders at minimum are 50 watt - many are in the Kilowatts and reek havoc on just about any radio or electronic device within a few hundred metres range , Thankfully they are not connected to antenna's so interference to other users on 27Mhz would be minimal given the 2 channel minimum gap if you were not next door.

[DevilDog66]

Yet again CBRT confirms why I love being a member. I had no idea about this "gap" on 23 channel CB's, learning something new everyday! Thanks for the post CB Docter and pabxone!

[G2527]

Good read for sure. Funny, as a kid using a 23 channel cobra cb, I thought I was getting an extra channel, like channel 24. Anyway very interesting post. Ty CB Doc

G~