> Alex Perry writes: > > Some units report all three digits, but designers usually want to save > > panel space and omit the unnecessary digit. Thus, for example, > > the ground control frequency for KMYF is 118.225 MHz but the radio > > actually displays "118.22" (a notam recently changed it from 121.9). > > The radio in 91R, the only one I've needed to use 25kHz spacing on, > > consistently rounds down, so that another frequency might be "119.77".
Dave comments: > I'm afraid I'm a touch confused here. How do you actually select > the 25kHz spacing if it is not displayed? Is there a different mode > of radio operation that you can get into where adjustment is in > 25kHz spacing and so the last digit can be inferred, and if so how > is this physically done? Well, there are some old radios out there that predate the change to 50kHz spacing and have _two_ switches sticking through the panel; the main rotary dial does 100kHz step, the first switch adds 50kHz (with no visual indication) and the second switch adds 25kHz on top. These are _really_ confusing to use and I suggest we don't model them. Most non-recent radios display two decimal digits, i.e. 10 kHz steps. Since the frequency spacing of 25 kHz is larger than the displayed step, it is always obvious what the frequency really is. Essentially, if the displayed number has a "2" or "7" in the hundredths position, then you have to imagine that it is followed by a hidden "5". When you turn the big knob, the whole MHz number changes in steps of one. When you turn the little knob, the fractional MHz number changes, with the display sequence 00 02 05 07 10 12 15 17 20 ... corresponding to the freqs 000 025 050 075 100 125 150 175 200 kHz I'm also not talking about the radios that support the modern frequency spacing of 8.333kHz that is slowly being adopted for commercial transport and will propagate down into general aviation in a few years. These radios all have to display all three digits, of course. Dave asks: > Additionally, some UK NDBs have the need for an additional digit > on the ADF display, eg 353.5 at East Midlands. How does this > work out in terms of tuning and displaying the frequency? No idea; they don't do that here and the ADFs I use don't support it. _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
