Todd, There are various reasons for using "Negative Loading circuits". If you are ineterested in maintining a high average modulation percentage without splattering from negative cycle over modulation, then may I suggest a few first steps:
1.) get your speech polarity correct since your voice on a scope is probablly asymetrical. 2.) Use some form of peak limiting (not hard clipping) in the audio chain. 3.) Use a scope while modulating to keep track of where you are. I like X;Y or Trapezoid mode for this. As far as modifying your transmitter to achieve the same end, lots do it, some sound like hell, and others work out pretty well. I prefer the approach that is transparent until a certain - modulation percentage is achieved, say 85% negative. At that point a combination of a bias supply, diodes, and resistors kick in to either load, or attenuate the negative cycle from that point on. The circuits that load the negative cycle all the time are the ones that in my opion sound like hell, and need to be avoided. I have used on a couple of rigs a circuit that I call PNCL, "progressive negative cycle loading", but that is another story. As for protecting your iron, a spark gap on the primary plate to plate might be better than one across the modulation transformer secondary...opinions? Regards, Jim WD5JKO --- "Todd, KA1KAQ" <[EMAIL PROTECTED]> wrote: > Just curious to get some opinions on these circuits, > the best design > to use, or if I should use one at all. > > Brett, I heard talking about the negative loading > cycle circuit > causing problems for you, I wonder if you could > explain more? It's > something I had thought about adding and have talked > with folks who > swear by them. Is there are good way and bad way to > do so, or is it > just a bad idea from the start? The initial reason > that interested me > was protection of the mod iron. > > ~ Todd/'Boomer' KA1KAQ > ______________________________________________________________ > AMRadio mailing list > Home: > http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul > Courson/wa3vjb >
