Impedence matching to cb radio

[Driverj30t9]

Yeah if I had to go with one radio in my truck I would go with a cb, but why have one radio when you can have two?

If they had the radio on to start with, they might not have gotten into the jam.*--- That's true. Also SSB has to be better at alerting you ahead of time because of the range.

I have bird perches so those hopefully will do the trick.

But we wouldn't have had all these people trying to run 1000 Watts, over-modulating, whistling, repeating "audio, audio, audio". ---How come? Wouldn't we still be doing all of that? Does amplitude modulation still work okay for 400 MHz and above? I think the military aircraft band goes to like 390 Mhz so if we did have UHF for cb radio in the states it would be a lot higher then the military band.

More than several miles while out on the highway isn't very useful.------Isn't it best to get the signal as far out as possible though just in case? I agree up to several miles is probably where it is most useful though. If there was a major traffic accident though 20 miles up the road I would want to know about as soon as possible so I could figure the best way to go around.

Gotta be careful asking directions over the cb because of individuals with bad intentions or that just wanna mess with you, send you to the wrong addreas, but that probably doesn't happen often, otherwise it'd be good. Just a key of the mic and your finding out what you need. Plus they have hands free laws with cell phones now but radios are still fine to use.

Yep, GMRS, FRS, and MURS. Not sure which channels require a license and which don't.

 

[FiveFilter]

I don't think it's the technical characteristics of the HF 11 meter band that makes CB so frustrating. It's the free-for-all multitudes that infect the band and make it hard for a serious use of it. I'd say any VHF and UHF frequency would have the same problem given the same rules and circumstances as apply to CB.

As the cartoon once said, "We've found the enemy, and he is us."

 

[Driverj30t9]

I suppose if people were disciplined enough to study for an exam and go take it they would be more disciplined radio operators. On the technical side if say they allowed 25W and it was FM people might not be adding amps so much and doing all those radio tests but I don't see what's bad about testing stuff. CB users in general just seem to be a lot more obnoxious then hams.

 

[Driverj30t9]

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As the cartoon once said, "We've found the enemy, and he is us."[/QUOTE] Don't believe I've heard that before but sounds correct.

 

[krokus]

I don't think it's the technical characteristics of the HF 11 meter band that makes CB so frustrating. It's the free-for-all multitudes that infect the band and make it hard for a serious use of it. I'd say any VHF and UHF frequency would have the same problem given the same rules and circumstances as apply to CB.."

Less issues with skip traffic.

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[AC9BX]

I don't think it's the technical characteristics of the HF 11 meter band that makes CB so frustrating. It's the free-for-all multitudes that infect the band and make it hard for a serious use of it. I'd say any VHF and UHF frequency would have the same problem given the same rules and circumstances as apply to CB."

I don't think so, perhaps to some degree. Overcrowding and people being jerks wouldn't have changed. But the number of them may. A great deal of the non-sense was CBers buying amplifiers, using them illegally, and often incorrectly, to talk by skip. Aside from some occasional atmospheric things once you get to VHF it's basically line of sight. There'd be little advantage in using all that power since you aren't going to get much beyond the horizon. CB would be local and regional, as was intended. There would still likely be abuses.

 

[AC9BX]

Also SSB has to be better at alerting you ahead of time because of the range.

Eh ... SSB is more power efficient. You may get some additional range compared to full AM. But it's not dramatic at these power levels. You have 12 Watts as the maximum Peak Envelope Power for SSB. Assuming perfect 100% modulation for AM, 4 Watts of max. carrier power equals 16 Watts PEP. But the power dissipation maximum of the output device is 10 Watts. So in either case the output can only achieve that briefly.

Does amplitude modulation still work okay for 400 MHz and above?

Any form of modulation works on any frequency. There's reasons why one is used versus another. Some of the reason is simply because that's how it was before.

I think the military aircraft band goes to like 390 Mhz so if we did have UHF for cb radio in the states it would be a lot higher then the military band.

Yep, up to 400Mhz, CB would be higher, as exists a CB band in Australia at 470Mhz. They intended to end the use of 27 MHz but that didn't go over well. The proliferation of US radios prompted many users in the UK despite not being legalized for 27MHz until 1981. They proposed a 900 MHz CB band.

More than several miles while out on the highway isn't very useful.------Isn't it best to get the signal as far out as possible though just in case? I agree up to several miles is probably where it is most useful though. If there was a major traffic accident though 20 miles up the road I would want to know about as soon as possible so I could figure the best way to go around.

Just a key of the mic and your finding out what you need. Plus they have hands free laws with cell phones now but radios are still fine to use.
Yep, GMRS, FRS, and MURS. Not sure which channels require a license and which don't.

FRS is unlicensed. GMRS currently requires a license but that may change. These 2 are at 462 MHz. A well working CB on a clean channel (which can be the most difficult part) can easily get to 20 miles. 2 Watt FRS channels with the handheld radio, outdoors, will cover several miles. The half Watt channels will cover a few. You can use up to 50 Watts on GMRS. So, 10 to 20 Watts for a 400 MHz CB band would be reasonable and effective. It's all just academic.

I used CB many times to provide and receive traffic info. Always helpful.

You have to be careful with these hands-free rules. Here in Illinois when they first proposed a ban intending to keep people off the phone they worded it "any communication device." Well, that bans everything. And it would have, any type of radio for any user, bus drivers, truckers, garbage collection, everything. They later amended it and it excluded everything except old phones. They then added more specific language insisting on hands-free devices.

 

[prcguy]

The peak power on AM is a little more than peak on SSB, but a typical AM receive band width is between 6 and 8KHz where SSB is around 2.4 to 2.8KHz. When you cut the receive BW in half you get a potential system improvement of 3dB and the difference between a 6KHz receiver and a 2.4KHz receiver is closer to a 4dB improvement.

Now take the difference in peak power from AM to SSB and you have a 1.25dB advantage with AM, minus the 4dB advantage for the narrower receive BW on SSB and you end up with an overall advantage of 2.75dB for SSB, not counting other factors I'm not aware of.

Going back to the late 1940s, the first CB that was allowed was Class B and it was at 462MHz and AM mode. Yup, UHF AM.

Eh ... SSB is more power efficient. You may get some additional range compared to full AM. But it's not dramatic at these power levels. You have 12 Watts as the maximum Peak Envelope Power for SSB. Assuming perfect 100% modulation for AM, 4 Watts of max. carrier power equals 16 Watts PEP. But the power dissipation maximum of the output device is 10 Watts. So in either case the output can only achieve that briefly.



Any form of modulation works on any frequency. There's reasons why one is used versus another. Some of the reason is simply because that's how it was before.



Yep, up to 400Mhz, CB would be higher, as exists a CB band in Australia at 470Mhz. They intended to end the use of 27 MHz but that didn't go over well. The proliferation of US radios prompted many users in the UK despite not being legalized for 27MHz until 1981. They proposed a 900 MHz CB band.





FRS is unlicensed. GMRS currently requires a license but that may change. These 2 are at 462 MHz. A well working CB on a clean channel (which can be the most difficult part) can easily get to 20 miles. 2 Watt FRS channels with the handheld radio, outdoors, will cover several miles. The half Watt channels will cover a few. You can use up to 50 Watts on GMRS. So, 10 to 20 Watts for a 400 MHz CB band would be reasonable and effective. It's all just academic.

I used CB many times to provide and receive traffic info. Always helpful.

You have to be careful with these hands-free rules. Here in Illinois when they first proposed a ban intending to keep people off the phone they worded it "any communication device." Well, that bans everything. And it would have, any type of radio for any user, bus drivers, truckers, garbage collection, everything. They later amended it and it excluded everything except old phones. They then added more specific language insisting on hands-free devices.

 

[FiveFilter]

.

As the cartoon once said, "We've found the enemy, and he is us."

Don't believe I've heard that before but sounds correct.[/QUOTE]

That quote comes from a Pogo cartoon series that ran in newspapers from 1948 to 1975. According to Wikipedia, it was revealed in a cartoon on Earth Day in 1971 when Pogo (a possum) and another animal encountered a bunch of trash in a forest which made a real mess of things. Pogo then used the enemy-is-us statement (although ironically, animals couldn't have actually put that trash in the forest; only we humans are smart enough to accomplish such a feat).

Unfortunately the statement applies to a lot of other human endeavors, including misuse of the CB.

 

[nd5y]

I suppose if people were disciplined enough to study for an exam and go take it they would be more disciplined radio operators.

Think again. Written tests don't keep the riff-raff out of ham radio. Neither did morse code tests.

 

[KC4RAF]

ND5Y made an excellent point about the test not keeping out the riff-raff. There's a thread on going right now to prove Tom's comment. Do a little check in the Amateur threads......
And thanks Tom for bringing that fact out to light.

 

[jhooten]

ND5Y made an excellent point about the test not keeping out the riff-raff.

Many of which hold 1X2 or 2X1 calls as evidenced by the the Extra sub-band on 80 meters.

 

[Driverj30t9]

QUOTE=AC9BX;2950962]Eh ... SSB is more power efficient. You may get some additional range compared to full AM. But it's not dramatic at these power levels. You have 12 Watts as the maximum Peak Envelope Power for SSB. Assuming perfect 100% modulation for AM, 4 Watts of max. carrier power equals 16 Watts PEP. But the power dissipation maximum of the output device is 10 Watts. So in either case the output can only achieve that briefly.[/QUOTE]

Okay so it may be better on range but not a whole lot.

Any form of modulation works on any frequency. There's reasons why one is used versus another. Some of the reason is simply because that's how it was before.[/QUOTE]

Alright, good to know.


Yep, up to 400Mhz, CB would be higher, as exists a CB band in Australia at 470Mhz. They intended to end the use of 27 MHz but that didn't go over well. The proliferation of US radios prompted many users in the UK despite not being legalized for 27MHz until 1981. They proposed a 900 MHz CB band.[/QUOTE]

That'd be interesting using both 27MHz and 470MHz. Guess the UK wanted to keep things more standardized with the U.S and others perhaps, could be why they didn't switch to 900MHz.

FRS is unlicensed. GMRS currently requires a license but that may change. These 2 are at 462 MHz. A well working CB on a clean channel (which can be the most difficult part) can easily get to 20 miles. 2 Watt FRS channels with the handheld radio, outdoors, will cover several miles. The half Watt channels will cover a few. You can use up to 50 Watts on GMRS. So, 10 to 20 Watts for a 400 MHz CB band would be reasonable and effective. It's all just academic.[/QUOTE]

I remember reading that one of the services had some free to use channels and other channels for the same service that need a license. Yeah that sounds about right.

I used CB many times to provide and receive traffic info. Always helpful.[/QUOTE]

Nice to hear about someone getting some good use out of it. I agree.

You have to be careful with these hands-free rules. Here in Illinois when they first proposed a ban intending to keep people off the phone they worded it "any communication device." Well, that bans everything. And it would have, any type of radio for any user, bus drivers, truckers, garbage collection, everything. They later amended it and it excluded everything except old phones. They then added more specific language insisting on hands-free devices.[/QUOTE]

Hmm, I shall tread carefully then. Thanks fpr the warning. Cop would probably love to slap a person with a large ticket for that. Always good to check the books on the states one will be driving through.

 

[Driverj30t9]

The peak power on AM is a little more than peak on SSB, but a typical AM receive band width is between 6 and 8KHz where SSB is around 2.4 to 2.8KHz. When you cut the receive BW in half you get a potential system improvement of 3dB and the difference between a 6KHz receiver and a 2.4KHz receiver is closer to a 4dB improvement.

Now take the difference in peak power from AM to SSB and you have a 1.25dB advantage with AM, minus the 4dB advantage for the narrower receive BW on SSB and you end up with an overall advantage of 2.75dB for SSB, not counting other factors I'm not aware of.

Going back to the late 1940s, the first CB that was allowed was Class B and it was at 462MHz and AM mode. Yup, UHF AM.

So how come AM has a receive BW between 6 and 8 KHz and SSB has a BW between 2.4 - 2.8 KHz? Is it the way the signal energy is re-directed?

I guess shortening the bandwidth of the carrier and modulated signal makes for a pointier wave increasing the amplitude and thus the decibels?

My understanding of all this then is that SSB is more advantageous for receiving then transmitting.

462MHz, haha, isn't that ironic. Wonder why they decided to go with HF instead.

 

[Driverj30t9]

That quote comes from a Pogo cartoon series that ran in newspapers from 1948 to 1975. According to Wikipedia, it was revealed in a cartoon on Earth Day in 1971 when Pogo (a possum) and another animal encountered a bunch of trash in a forest which made a real mess of things. Pogo then used the enemy-is-us statement (although ironically, animals couldn't have actually put that trash in the forest; only we humans are smart enough to accomplish such a feat).

Unfortunately the statement applies to a lot of other human endeavors, including misuse of the CB.[/QUOTE]

Ahh yes, humans the most destructive species the world has known. Good though even if it makes just a few people think about their actions.

Unfortunately, life is not without struggle that's for sure.

 

[Driverj30t9]

Think again. Written tests don't keep the riff-raff out of ham radio. Neither did morse code tests.

ND5Y made an excellent point about the test not keeping out the riff-raff. There's a thread on going right now to prove Tom's comment. Do a little check in the Amateur threads......
And thanks Tom for bringing that fact out to light.

Many of which hold 1X2 or 2X1 calls as evidenced by the the Extra sub-band on 80 meters.

There's gotta be less of those types though. As bad as CBers? Can't see a lot hams with their amp cranked up rambling a bunch of non coherent sentences or cussing each out. I'm sure it happens occasionally but not like regularly on CB where it's like the norm.

I don't mind it, a person can always change the channel or turn the volume down if they don't care to listen.

I"ll give the thread a look.

 

[krokus]

So how come AM has a receive BW between 6 and 8 KHz and SSB has a BW between 2.4 - 2.8 KHz? Is it the way the signal energy is re-directed?

I guess shortening the bandwidth of the carrier and modulated signal makes for a pointier wave increasing the amplitude and thus the decibels?

My understanding of all this then is that SSB is more advantageous for receiving then transmitting.

462MHz, haha, isn't that ironic. Wonder why they decided to go with HF instead.

You have the basic understanding, the details are a bit more involved. Here is a simplified version.

For AM, the voice generates upper and lower sidebands, with the carrier still present. SSB starts as AM, then the unwanted sideband is filtered off, along with the carrier. The wanted sideband is amplified, and transmitted. That is why the BW for AM is slightly more than double the SSB is.

Receiving AM is simple, the signal is applied to a detector, and the audio recovered. SSB has the carrier re-added, then those signals are sent to the detector.

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[AC9BX]

So how come AM has a receive BW between 6 and 8 KHz and SSB has a BW between 2.4 - 2.8 KHz? Is it the way the signal energy is re-directed?

I guess shortening the bandwidth of the carrier and modulated signal makes for a pointier wave increasing the amplitude and thus the decibels?

My understanding of all this then is that SSB is more advantageous for receiving then transmitting.

AM creates 2 sidebands. SSB is single sideband. Technically it's single sideband suppressed carrier. For the same audio range, say 3kHz which is all that's needed for understandable speech, full AM is twice as wide plus a carrier. SSB is more energy efficient in this regard. The same amount of power can be applied to less bandwidth. So the result is an effectively stronger signal. For receiving because the bandwidth is more narrow there is also less noise to deal with, thus more narrow bandwidth can be more effective at that end. Regardless of mode the receive bandwidth should equal the transmit bandwidth to hear the signal completely without extra noise. Going more narrow on receive can help in reducing noise but it also removes part of the signal.

Mathematically the carrier, true for sending code as well, has zero bandwidth. In practice it doesn't work that way. The carrier is a signal on only one frequency. Bandwidth is the difference between 2. One minus one equals zero.

 

[Driverj30t9]

Okay, good stuff to know. I'm going to go with my first SSB CB on this mobile setup. Most likey some model of Uniden Bearcat even though I like the Cobra, they don't have a scanning SSB radio that I'm aware of.