By 'tilt' I mean the observable tilting of the top and bottom of a square wave (or resulting modulated envelope) caused by low frequency roll off and non constant group delay through the transmitter in question. Ideally what you want is waveform fidelity, what goes in should come out. The closer you can get to this ideal the better. Square wave tests are very useful as they will tell you a lot of info in one picture, and many hams have function generators available, (and if you operate AM you should already have a scope).
This tilt will increase the peak voltage of the incoming waveform. This in turn will force you to reduce your average modulation level to keep the increased peak level from overmodulating the transmitter. The same result happens from any ringing or overshoot the system may have. Where this becomes a significant issue is if you try to drive this poor performing xmtr with waveforms that have flattop components, typically produced by audio clipping. You end up fighting yourself as you just increased your average level with the clipping, but are then forced to turn it down again to some extent by the inability of the xmtr to pass the waveshape. Since some degree of peak control is necessary to prevent negative overmodulation (and the resulting splatter and unneighborly excessive occupied bandwidth), this all conspires against you to produce a less than fully modulated signal. There are some low level audio gimmicks that can be applied to partially compensate for this, but it's always best to go after the root cause and improve that first. Granted this is only ham radio and it's not a big deal if everything isn't optimized. But it's interesting to look at all this and try to improve things, and it gives us something else to talk about on the air other than politics! I'm looking for some helpful pictures for you but haven't located any at hand. FWIW, you might look at Fig. 2-9 on page 2-22, and Fig. 2-10 on page 2-24 of the operating manual for the Orban AM Optimod 9100B, which is on their FTP site here: ftp://ftp.orban.com/9100B/9100B_Manual_Section_2.pdf That may help make it more clear. g Byron Lichtenwalner wrote: > > Gary > I have read several of your writings that refers to "tilt". What is it, or > where can I go to learn more about it? > Byron W3WKR
