On Mon, Feb 14, 2011 at 12:07 PM, Bob McGwier <[email protected]> wrote:
> It is all software. > > The DSB suppressed carrier, fully complex signal is made just like any > other > DSB signal would be. This is added coherently to the carrier. Since you > are not modulating the envelope of the carrier, but adding two coherent > signals, this allows the supermodulation AM you have discovered. You are > the first I KNOW ABOUT to have expressed all of this so clearly. The > "200%" modulation stuff in your videos is something I have not thought > about > since I never dreamed anyone would go that high. > > Congrats. > Duh. Like many things, it is obvious when you think about it ... after someone else points it out. I always knew that the power increased as a function of the modulation (sideband) power being added to the carrier power but my brain switched off because I kept thinking in terms of equal positive and negative voltage deviation from the carrier baseline when, in fact, the average voltage level must shift upward to accommodate the increased average power level. This results in the appearance of higher positive peaks than negative peaks when in fact it is just an increase in the average power by 25% from the modulation power being added to the carrier power. And this has nothing to do with DSP. This should happen with ANY AM transmitter that is being modulated properly. I suspect that the reason it doesn't for some is that the PA is getting into compression on peaks. Thanks for the lesson and reminder Bob. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 [email protected] +1.767.617.1365 (Dominica) +1.931.492.6776 (USA) (+1.931.4.WB6RQN) _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software.
