On Fri, Jun 3, 2011 at 10:41 AM, Mitch Baum <[email protected]> wrote: > 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. >
True. However, the standard for representing a signal is center frequency and bandwidth. Only amateur radio does not adhere to this. > 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. > Yes, you can represent it that way. The problem is, there is no standard for the offset from the "vestigial" carrier frequency. So knowing that "vestigial" frequency does not help you determine whether you are in-band or not, at least not unless you know the subcarrier offset from the "vestigial" carrier. > 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 agree. But then we also have requirements for signal purity to which we must adhere as well. > > 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. Yes, that is extremely useful in visualizing what is going on. I think it is telling that it makes no reference to the transceiver VFO frequency (vestigial carrier) as that is irrelevant. > 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. That is a fault and a different problem entirely. > 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. > Oh, I do look. And I know how to make fldigi jump through almost any hoop. That is not the point. The point is, and I make it once more, VFO frequency by itself, does not give you particularly useful information. >From a UI point of view, doing something like dragging the background of the waterfall would change the rig LO injection frequency (VFO) and cause the channel center frequency to change. Moving the cursor/lubber-line would change the subcarrier frequency. And then, one could move both at once, causing the channel center frequency to remain constant even though both vestigial carrier and subcarrier frequencies are changing concurrently. Integration of CODECs/modems and the tunable IF (rig) is becoming tighter as time goes by. I cannot even begin to imagine going back to the way we did things even a few years ago. What I am suggesting is that it is time to begin thinking about how this integration changes our view, whether we like it or not, whether it is conventional or not. So, given these changes, what is the impact on the user interface? A key issue is helping the operator to visualize his/her actual RF emission without having to do a bunch of mental arithmetic. The computer is ever so much better at that sort of thing than we are. (And I am darned good at doing mental arithmetic.) I am suggesting (strongly -- did you notice?) that it makes more sense for the UI to display information in terms of center frequency and bandwidth than it does to display VFO frequency, which is not useful unless you also display audio subcarrier offset. If you are like me, you set the waterfall in RF frequency display mode, not audio frequency display mode. (And, yes, displaying operating frequency and bandwidth limits in the movable cursor is great, thank you.) Knowing the VFO/vestigial-carrier/LO-injection frequency just doesn't appear to me to be that useful unless I want to add the VFO frequency to the audio subcarrier frequency in my head. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 [email protected] +1.767.617.1365 (Dominica) +1.931.492.6776 (USA) (+1.931.4.WB6RQN)
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