The QSO Frequency shows you the "Center" frequency or in more exact terms, the actual operating frequency if you were to assume no frequency modulation as in CW.
The term "Center Frequency" has little if any valid use as this is of little value when one considers that most digital modes are not a "Return to Center" mode and each mode has its own occupied bandwidth. If we were to assume that one might want to know if you are operating with any portion of your signal outside of an authorized frequency then one needs to know the radio dial frequency (this is the vestigial frequency of the carrier if one were to be transmitted) and the upper and lower limits of the modulating signal ( equivalent to the "sidebands" as it were. Given that all of this is displayed clearly in the current fashion, and every licensed amateur should be able to determine if he/she is operating within the authorized frequencies, I would suspect that the only enhancement could be a pop-up tool that would simply display the center frequency (Dial frequency plus or minus the audio center frequency depending on USB or LSB mode) and the upper and lower transmitted frequencies (based on the mode and occupied bandwidth for the selected mode). This might allow for a quick view of whether or not one is operating with signal elements that "MIGHT" be outside of authorized frequencies. I say "MIGHT" because any non-linearity in the signal path or modulating circuits could make the actual signal wider than a "calculated" value based on the above information available. I for one have come to appreciate that Dave and crew have taken great steps to keep the user interface uncluttered and present the important information as exactly and clearly as possible. The signal bar lines drawn on the waterfall show very clearly the upper and lower limits of the transmitted (or received) signals if the "monitor transmit" function is enabled. This presents the low level (baseband) spectra as closely as possible. Remember something as simply as a failing power supply filter capacitor could cause unintended modulation resulting in a wider than calculated signal. Other signal filters and components can cause similar effects that could not be calculated, but are present in the resulting signal. If one were to design such a pop-up, then I would hope to have a place to add "margin" values that would be added and subtracted from the lower and upper frequencies calculated so as to provide the user with an adjustable guard band for those band edge operating situations. The data is all there for you if you care to look. All that is missing is that for this to work, you must have working RIG CONTROL. Mitch Baum / AF2M / _______________________________________________ fldigi-alpha mailing list [email protected] https://lists.berlios.de/mailman/listinfo/fldigi-alpha
