what is "asymmetrical modulation" ?

[HiDef]

freecell,

what is your opinion of compressing the negative peaks of an AM signal so they cant exceed 100% and allowing the positive peaks to exceed 100%?

LC

You can already do that by using the correct polarity on better transmitters. Better meaning good frequency response and low ratio modulation transformers in the high level types.

One big drawback is the other guy's receiver. Most diode detectors produce unwanted distortion at higher positive peak levels. DSP is being used more and more so we may hear more "ultramodulated" stuff on the air someday. It certainly does sound louder.

A good writeup appears in OCT 1956 QST IIRC.

 

[HiDef]

I think NU9N got the overmodulated labels for low-level and high-level backwards.

High-level is where modulation power is applied to the DC power of the final(s). Also known as "plate modulation".

Low-level is where modulation is applied before the final amplifier and then amplified by linear devices.


When you over-modulated on a high-level design, the output signal will appear as double-sideband reduced carrier, but not splattering.
Its the low-level design that splatters on >100% negative peaks.

NU9N has it correct. High level meaning high power modulator in series with DC supply to class C R.F. stage. The one polarity of the AC will cut the carrier off if the AC voltage exceeds the DC supply voltage to the R.F. amplifier.

Low level assumes a balanced modulator in his pictures. You can't cut off the carrier with a balanced modulator. It simply starts modulating in the positive direction.