I agree completely, unfortunately my laziness is the culprit here. The plate and screen modulation transformers have no secondary center taps, I was too lazy to re-do the symbol, that is, I am not very good at CAD and don't know how to do this properly yet.
But this is more than worthwhile, I will look into using a different transformer for the screen, I have several, and one might make a mutch better match as your calculations clearly show. I think I have a 50W multimatch around somewhere that would do a better job with the turns ratio than that big 125W bugger. Thank you, Patrick > From: "John Coleman, ARS WA5BXO" <[EMAIL PROTECTED]> > > Hi Patrick > It looks as though you have made all the right calculations. > But keep in mind that the purpose of the screen modulation transformer > is to lower the audio voltage going to the modulator and its design > impedance is of little importance. Its turn ratio is of most concern. > And if I may make two assumptions here then there might be some > simplification. > Assuming that the secondary of the modulation XFMR and the > screen modulation XFMR have a 50/50 split, then consider starting with a > lower audio voltage by using the center tap of the modulation XFMR as > the take off point for the screen audio. This voltage should be 1/2 of > the audio voltage of the top point. Then consider using only half of > the secondary in the screen modulation XFMR. You can only do this if the > primary of screen modulation XFMR can handle the higher primary audio > voltage which will of course be twice as high as before. The dropping > resistor is then much smaller and much less heating and loss involved. > > I took the liberty of recalculation all the parameters for using > 1/2 of each XFMR secondary which you can view at > http://wa5bxo.shacknet.nu/HAMPICTURES/mod002.GIF
