AM power

Discussion in 'Amplitude Modulation - AM Fans' started by N2RDQ, May 15, 2018 at 6:27 PM.

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1. N2RDQHam MemberQRZ Page

Can someone explain the math behind the "375" watts AM being 1500 watts pep ( pep = 4x am power)?

I know it been a while since I was in engineering school but, as I remember it...
at 100% modulation, sidebands were 25% of the carrier power each for a total of 50% peak.

so at 100% modulation, with 1000W carrier + 500W peak for the sidebands = 1500W

Also, AM isn't measured in PEP anyway...

where am i wrong?
How is the carrier different from CW power, and how are the sidebands different from SSB peak power?
I just don't get this 4X thing at all. I know there's something I am missing, there must be.

3. N2DTSHam MemberQRZ Page

Sounds fine to me, 1000 watts carrier and some wimpy sidebands.

If you look on a peak reading watt meter, with a typical good transmitter, a 400 watt carrier will hit 1500 watts pep.
But if you turn the variac up to 1000 watts carrier, who is to know?

4. K3XRHam MemberQRZ Page

"Character is doing the right thing when nobody's looking. There are too many people who think that the only thing that's right is to get by, and the only thing that's wrong is to get caught."

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Phil

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6. WA3VJBHam MemberQRZ Page

Hey Phil, I know it was unintentional on your part, but that PDF perpetuates in a subtle way some anti-AM propaganda that was used to help SSB's struggle for acceptance years ago. RDQ, being schooled in engineering, likely appreciates the formulas and other discussion. But this paragraph I'll gladly dispute as judgmental and erroneous.

So SSB or Single Sideband modulation was developed to reduce bandwidth and to carry the same intelligence. For voice, SSB can carry the same information in a 3.5kHz bandwidth, and only amplify the intelligence information for transmission, without wasting carrier power...

And with the audience here on the AM Forum, I won't recite why the above paragraph is wrong, was always inappropriately pejorative, and should be disregarded.

7. AC0OBSubscriberQRZ Page

That sentence wasn't meant to be pejorative, voice an opinion, or otherwise, but Historical in nature only.

Phil

Last edited: May 15, 2018 at 8:25 PM
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8. WA3VJBHam MemberQRZ Page

Well, then this is for you. Having a carrier is not a "waste," as judged in the document, since the carrier contains information useful to a listener such as pacing, punctuation, and as a cue a transmission has ended. The arbitrary passband that was mentioned does not fully replicate the information and technical support of reception of a wholesome AM waveform. Consider the effect of quieting and AGC operation, as two contributions, as well as a source for synchronous detection. And of course, having both sidebands in a wholesome AM waveform further empowers a listener to select the passband with minimal interference away from center frequency.

9. KB4QAAXML SubscriberQRZ Page

There is nothing derogatory in that statement. Purely factual.

10. K4KYVSubscriberQRZ Page

It's a long story, explained in full detail here, with exhibits of pertinent official documents:

Part 1: Chronological time line 1983-1990, Exhibits 1-9
https://ecfsapi.fcc.gov/file/11142326307940/17110802.pdf

Part 2: Exhibits 10-16
https://ecfsapi.fcc.gov/file/11142326307940/17110802-2.pdf

Also fully documented here with additional material. Read the entire thread of messages, and view each of the attachments. Then come to your own conclusions.

Depending on how you define the "right thing". Especially considering that the "thing" was dumped on us; "character" is indeed an issue since the whole proceeding was fraudulent to the core. Read the full history from the beginning to the end, including all the exhibits, and decide for yourself.

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