It's too bad we can't try it.
However, the skip would have to
be just right.
On the upper channels, either 35
though 40, or 36 through 40, I
have heard many civilized conversations
with the ops using SSB.
The ones I have heard don't even
say "10-4." They say "roger" instead.
Bruce, SLUG 88.3
The same spacing issues used to make me wonder, too, Carl. If you notice, that up to channel 22, the channels seem to be in banks of 4 together (10 KHz apart) and then a gap, like between 3 and 4, 7 and 8, 11 and 12, 15 and 16 and 19 and 20. My dad was an over the road trucker in the 1960s, 1970s, 1980s and the 1990s and he was always trading/upgrading CBs that had extra channels, below channel 1, above channel 40, and in-between channels (3A, 7A, 11A, 15A, and 19A. The theory behind that was the "un-used or less-used" frequency would be clearer, with less radio traffic interference... My understanding was whe CB was first allotted the 23 Channels, they left a gap between 22 and 23 for old garage door openers (operating class C transmitters). My grandpa used to open and close the garage door at his shop with a CB on 24 or 25...Then when the FCC gave 17 more channels to CB, they used every single space, starting with 24 and 25 between 22 and 23, then carrying on from 26 to 40 with no gaps, effectively using every single frequency available...I was HUGE into CB until I turned 14, then got my first Ham ticket, Novice, which I held for over 20 years before upgrading to General class...
Dave VQX
The same spacing issues used to make me wonder, too, Carl. If you notice, that up to channel 22, the channels seem to be in banks of 4 together (10 KHz apart) and then a gap, like between 3 and 4, 7 and 8, 11 and 12, 15 and 16 and 19 and 20. My dad was an over the road trucker in the 1960s, 1970s, 1980s and the 1990s and he was always trading/upgrading CBs that had extra channels, below channel 1, above channel 40, and in-between channels (3A, 7A, 11A, 15A, and 19A. The theory behind that was the "un-used or less-used" frequency would be clearer, with less radio traffic interference... My understanding was whe CB was first allotted the 23 Channels, they left a gap between 22 and 23 for old garage door openers (operating class C transmitters). My grandpa used to open and close the garage door at his shop with a CB on 24 or 25...Then when the FCC gave 17 more channels to CB, they used every single space, starting with 24 and 25 between 22 and 23, then carrying on from 26 to 40 with no gaps, effectively using every single frequency available...I was HUGE into CB until I turned 14, then got my first Ham ticket, Novice, which I held for over 20 years before upgrading to General class...
Dave VQX
Some of those "unused" channels are for R/C controls such as the door openers you mentioned and remote control of hobby models (car, airplane, etc.)
part 95(d) citizens band goes from 26.965 to 27.405 in 10 khz increments covering 40 rf channels centers.
those pre 40ch era unused channels are now used to make up the 40 channels.
Here is a list of CB frequencies. You'll notice "skips" between
3 & 4, 7 & 8, 11 & 12, 15 & 16, 19 & 20, and 23 is out of order.
This skips are where the R/C and other uses remain.
This keeps the original 23 channels compatible with the older 23 channel CBs.
I checked two different sources and they are the same.
CHANNEL FREQUENCY
1--26.965 MHz
2--26.975 MHz
3--26.985 MHz
4--27.005 MHz
5--27.015 MHz
6--27.025 MHz
7--27.035 MHz
8--27.055 MHz
9--27.065 MHz
10-27.075 MHz
11-27.085 MHz
12-27.105 MHz
13-27.115 MHz
14-27.125 MHz
15-27.135 MHz
16-27.155 MHz
17-27.165 MHz
18-27.175 MHz
19-27.185 MHz
20-27.205 MHz
21-27.215 MHz
22-27.225 MHz
23-27.255 MHz
24-27.235 MHz
25-27.245 MHz
26-27.265 MHz
27-27.275 MHz
28-27.285 MHz
29-27.295 MHz
30-27.305 MHz
31-27.315 MHz
32-27.325 MHz
33-27.335 MHz
34-27.345 MHz
35-27.355 MHz
36-27.365 MHz
37-27.375 MHz
38-27.385 MHz
39-27.395 MHz
40-27.405 MHz
As was said, CB is regulated by fcc 95.407.
But several part 15 rules overlap with CB.
15.225 includes the special allowance of 13.560mHz, shortwave, field strength may not exceed 15,848 microvolts/meter at 30 meters.
As it so happens the second harmonic of 13.560 is 27.120mHz, which falls between CB channels 13 and 14, closest to channel 14.
When I first ran the Big Talker shortwave transmitter at 13.560, a buddy picked up my station on channel 14 of his CB radio.
Another rule is 15.227 which allows operation in the band 26.97 to 27.98mHz, field strength not to exceed 10,000 microvolts per meter at 3 meters. This spans CB channels 1 to 27.
Whereas under 15.225 the 2nd harmonic of 13.560mHz would normally need to be attenuated at least 20dB below the main carrier, since that 2nd harmonic falls within the scope of 15.227 it could be counted as being in that second category and possibly make a 13.560mHz transmitter a dual frequency transmitter under part 15.
Of course in the medium wave band there are some frequencies where this dual frequency operation might be possible... Let's say that 600kHz and 1200kHz (the 2nd harmonic) are both clear in your area. Then one transmitter could be designed to serve both frequencies, as if you had two transmitters.
As it gets to be more fun the confusion rises accordingly.
...CB trivia.
about that big space between
channels 22 and 23:
(In the "before times" when the
CB channels went up to only "23...")
I vaguely remember seeing either
Lafayette or Radio Shack with info
about two "new" CB channels. They
were something like HELP-1 and HELP-2,
or maybe HELP-A or HELP-B. They might
have been slated to go to that
"in between" space between 22 and 23.
at that time.
Also, I think channel 23 was allowed
a power of 250 watts under certain
conditions. Radio control? I don't
remember. I'll have to look that one up.
Bruce, 1020 CC
P.S. HERE"S A SECRET MESSAGE TO CARL
BLARE. RIGHT NOW AS WE SPEAK, I AM HAVING
COMPUTER PROBLEMS. (Several actually.)
I WILL GET BACK TO YOU AS SOON AS I CAN GET
THESE GLITCHES FIGURED OUT.
Let me crank up the volume....
I HEAR YOUR SECRET MESSAGE, CC 1020!! GET THAT MACHINE FIXED !!
One thing about the CB rules I think about....
Somewhere in there it says that you "cannot patch the CBcast through to a radio station to make a direct news report.
But you CAN send a news report by CB to the station, which the station can write down and deliver to their audience.
That really should be changed.
That's an interesting rule, Carl,
about the news feed thing.
That may go all the way back to
1958, when 27 MHz CB got started.
It's too bad that the FCC couldn't have
put CB up on something like 40 MHz
or 72 MHz, or something like that -
back then. I know there were probably
plenty of reasons then, why they COULDN'T,
but 27 MHz is a horrible place, really, if
you want to get real business communications
done.
Of course, NOW, it's just a goofy band to listen
to. I have been listening to channel 19 for probably
over a month, just for the humor of the thing.
The original class A CB from 1947 (?) was
BONKERS. I saw a picture of one of the
original 460 MHz class A CB radios.
I'll have to look at that picture again
and try to describe it in another post.
Bruce, 1020 CC