[Amps] Amplifier Vs Plate Modulated

[Fuqua, Bill L]

  Most all old amplifiers were spec. at 40%  carrier for AM compared to CW. 
I did say the limits were plate dissipation or PEP output, the lesser of the two.
I had to go back and take a look at waveforms. With full carrier single sideband you 
need to keep the sideband power level to less than 50% and to keep envelope detectors
happy is should be 25%.
  Diode detectors if operated as ideal square law detectors introduce considerable distortion.
Fortunately, most AM diode detectors are operated lots of drive, thanks to IF amplifiers and AVC,  and the drop across the
diode is small in comparison to the output voltage. 
  Now saying that CHU uses full carrier SSB. I need to take a look at that and 
I recall many years ago that one SSB transmitter emulated AM by just injecting carrier with
one sideband. But I can't recall where I saw it. You have to remember those were the
days that there was little concern about distortion.

  73
Bill wa4lav

________________________________________
From: Amps [amps-bounces at contesting.com] on behalf of Paul Baldock [paul at paulbaldock.com]
Sent: Wednesday, December 02, 2015 5:55 PM
To: Amps group
Subject: Re: [Amps] Amplifier Vs Plate Modulated

I assure you that AM is alive and well.

You might also consider that most older amps (not all) when you are
not speaking on SSB have 0% efficiency, and around 300W to 400W plate
dissipation.

You may have noticed that on AM many operators talk and talk and
talk. You probably thought they were just long winded. But no, they
are just trying to keep the efficiency up.

- Paul KW7Y


At 10:40 AM 12/2/2015, Bill Turner wrote:
>------------ ORIGINAL MESSAGE ------------(may be snipped)
>
>On Mon, 30 Nov 2015 23:34:01 -0600, Gary wrote:
>
> >With AM at 375 watts carrier out and no modulation, the efficiency of that
> >amp will be around 30%. That requires the input power to be 1250 watts. That
> >leaves 875 watts of plate dissipation with no modulation present.
>
>REPLY:
>
>And this is one reason why AM has become mostly a curiosity.  :-)
>
>73, Bill W6WRT
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