I guess it's a question of semantics, then.
To me, NPC was ONLY a way to keep the carrier alive. I didn't WANT it doing anything to my RF waveform.
When you look at the NPC mod for the series modulated transmitters (Galaxy, Cobra, etc), you'll see it hooks the audio waveform JUST above a diode.... That diode is going to cause problems with rectification of the AC component, and will cause problems with bleed as well... Just as pretty much any other circuit will.
What Shockwave is looking for with NPC is Assymetrical Modulation. That's too easy to accomplish nearly with phasing the microphone correctly! When you find the phasing on your mic that allows 125 percent pos peaks and 90 percent neg peaks, you THEN increase the audio to where you BARELY bump this circuit into conduction. You will then be at or over 150 percent positive peaks, and sounding like crap in nearly all receivers.... Especially when you are receiving on a simple diode detector. Add MORE distortion when the guy receiving has his noise blanker on.
This circuit is in current use on a pair of 4-1000s modulating a single 4-1000. That's a LOT of positive modulation capabilities, and it's being run as described above. You can't perform a lot of trickery in the transmitter itself to get assymetrical mod... You need to accomplish that via the modulator and (pre)driver to the audio stages.......
The problem you guys see with the rise and fall times of the mod waveform causing problems with distortion on the transmitted signal generally is indicative of the actual modulator (audio chip) running out of steam, or the transformer being undersized for the modulator.... It can also be caused by the wrong turns ratio for the transmitter, but not as bad.... I want to play with PAGING transformers, the 70V kind... Some are fairly cheap, have decent audio specs and will handle a hundred or more watts....
Anyway, this wasn't meant to GIVE you assymetrical modulation... That's something you get in the audio chain. This circuit is designed to eliminate the problems associated with running the carrier to 0 volts and the associated distortion with that.... It's not designed to be driven into conduction constantly.
--Toll_Free
