No pardon needed, Gary, and I appreciate your comments. I was only
correcting what Paul said:

AIUI the specified 4 Watts is the maximum*average* power allowed (in
the UK, anyway). When you modulate it 100% AM., it's still 4W average
power. . .

What's true is that the average *carrier* power is still 4 watts. But
that's not what the posting said.

I think it's important to be careful with our terminology. The problem
with being loose and free with it is that it causes us to keep having
breakdowns in communication. It also ends up giving people a mistaken
idea about how things work. A naive reader could easily take Paul's
statement to mean that the average power of a 100% modulated 4 watt
carrier is 4 watts -- that's what he said, after all (even though it
might not be what he meant). The lengthy discussion about "RMS power"
illustrates just how deeply rooted a misconception can get, simply from
being careless with terminology.

If anyone considers this to be just nit-picking, that's ok. If you
already understand it, just ignore my postings. But I hope it does serve
a positive purpose for some readers.

And I'm guilty, too! I should have said that the average power of a 100%
amplitude modulated 4 watt carrier is 6 watts *if the modulation is a
sine wave*. When modulated by voice, the average power over any given
interval can vary a great deal. That's why PEP is a more useful
measurement of the modulated signal. As Ian humbly pointed out, it's
really easy to be careless with terminology, and we all make mistakes.
But I think we should keep trying to do better.

Roy Lewallen, W7EL

Gary Schafer wrote:

Pardon my saying so Roy, but I think you may be confusing the issue
here. We all know that you understand this stuff backward and forward
and most here have the highest regard for your expertise, including
me. I also agree that you are totally correct in what you say.

The question was not what is the average power of a 100% modulated 4
watt carrier.
It was "is the 4 watt maximum power of a CB radio actually average
power, not RMS right?"

He is trying to establish the meaning between so called (widely
misused) RMS power and average. And he is also trying to figure out
the relationship to pep.

Although you did acknowledge that he has the correct conclusion to his
question, at the same time I think that you have injected some doubt
in your answer. There are a lot of people that have trouble with some
of the basics of this stuff. Throwing a little twist like that in
often raises the confusion level with some. Again pardon me for
comments.

73
Gary K4FMX


On Wed, 20 Oct 2004 13:17:49 -0700, Roy Lewallen
wrote:


The average power of a 100% modulated 4 watt carrier is 6 watts, not 4.
(If you want to look at it in the frequency domain, where the total
power has to be the same as in the time domain, you've now got the
original carrier plus two sidebands. The power in the two sidebands
totals 2 watts.) And I'd give the answer to Chris' two questions as yes.

Roy Lewallen, W7EL

Paul Burridge wrote:


On Wed, 20 Oct 2004 12:08:59 GMT, "Chris"
wrote:



Paul,

I've been following the thread still. Let me go back to the original
question for a moment. So is the 4W maximum power of a CB radio is actually
average power, not RMS, right? If it is modulated at 100% with a sine wave,
what wil the PEP be? Is 16W the correct answer?


AIUI the specified 4 Watts is the maximum*average* power allowed (in
the UK, anyway). When you modulate it 100% AM., it's still 4W average
power. If you fully modulate it with FM., it's *still* 4W average
power. But as you've seen here, for every assertion, there's a
contradiction. ;-)