Nice write up John! Hmm, AM with reverse carrier control. Sounds interesting. That would look something like an FM signal but with only one set of side bands.
Actually I have worked on some marine radios in the 70's that did do some reverse carrier control. They were SSB radios with AM capability. You could set the AM carrier level just about any level and when you modulated it would adjust the carrier down to the proper level. It was hard to make the radio sound bad on AM. I don't remember how the ALC was detected for the AM mode or exactly how the carrier level was controlled. I don't know if it would gain much but it would eliminate a little band noise when there was no modulation. ASYMMETRICAL AUDIO The fact that most of our voices are not symmetrical can be an advantage or disadvantage when modulating a radio. If the positive peaks are higher than the negative peaks then you will not over modulate in the negative direction while having positive peaks that exceed 100%. However if you are trying to run the legal limit power then it can be a disadvantage. Your average modulation level must be held low in order that the positive peaks do not cause you to exceed the power limit. Flopping the envelope over so that the negative peaks are higher than the positive doesn't help either. In that case you will over modulate before your average modulation level gets very high. The solution may be to make the modulation "more symmetrical". There are circuits consisting of several "all pass" filters that are supposed to do that. By having more symmetrical audio to modulate the transmitter with you will be able to obtain higher average levels of modulation without exceeding the power limit and not over modulating in the negative direction. It can also greatly reduce the need for large headroom in the modulator. Now add a little peak clipping and compression to the audio! You can increase the average audio even more while still keeping within the power limit and not over modulating in the negative direction. The broadcasters do it every day and most sound great. Of course it can't be overdone or it will not sound great anymore. Average power is what does the work in the audio. Those high sharp peaks are all but wasted. They add little to the sound of the signal. Especially on a crowded band. It is those high peaks that keep you from attaining the high average power that does most of the work. In RADAR there is a very high peak power to average power ratio. The reason being is that a certain pulse width and is needed to get the resolution. With a given pulse width the only way to increase the average power is to increase the peak power. Keeping the peak power the same and increasing the pulse width raises the average power which increases the range of the radar. But as the pulse width is increased the resolution gets poorer. (ability to distinguish between two targets) The point here is that it is average power that is important. 73 Gary K4FMX "John E. Coleman" wrote: > I've be working on a document that might be of interest to many folks. > With the help of K4KVY, WA3WDR, W5TOB and a month or two of night work > I've come up with something good I hope. Anyway here it is. > > http://www.qsl.net/wa5bxo/asyam/aam3.html > > I hope it is of some use to someone and encourages experimentation. > > John, WA5BXO > > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
