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4.4 - Tuning -- the details

Depending on what you want to receive, one way to tune is to adjust the receive frequency by Left-click or Right-click on the digits of the frequency displays. There are two of them; the lower one defines the center of the displayed bandwidth; the upper one allows you to select any frequency that is currently in the displayed bandwidth.

ZoC (Zero-on-Click) affects how this works; if ZoC is on, then all digits to the right of the one you are clicking on change to zero as soon as you make a change to any digit. If ZoC is off, only the digit you are clicking on changes.

Another way to tune is to click along the top row of tuning buttons. Also, Left-click CTR will lock the tuning position and scroll the signal display and waterfall instead of moving the demodulator along the signal display. If you're stepping through a broadcast band with < 5k, > 5k, < 9k, > 9k, or < 10k, > 10k, Right-click on any of those buttons will re-center the tuned point. This will work best with CTR. Left-click and holding will result in the tuning operation repeating automatically.

Likewise, PAN changes how the < W and W > buttons adjust the center and demodulator tuning. You'll find PAN on is a good way to work through a broadcast band, especially when generally tuning in 5, 9 or 10 KHz steps.

Another way to tune is by simply pointing and clicking on the waterfall or the RF signal spectrum display. Note that the Mouse Click Resolution settings in the DSP dialog affect how tuning operates when you're clicking on the spectrum or the waterfall.

Another is using keystrokes: See the tuning keystroke reference, below, or press Ref on the control panel.



Span Control

The displayed bandwidth for the signal display itself depends upon two things: First, the bandwidth set with SDR (50, 100, 150 or 190 KHz for the SDR-IQ) if you are receiving, or the bandwidth of the recording you are loading (for instance, you can handle a much wider NETSDR recording even if you only have an SDR-IQ), or the bandwidth set in the FUNcube configuration dialog ( Right-click FCD); and second, the Span, set with the S+ and S- controls at the left side of the SdrDx control panel, or with the  O and  P keystrokes.

if ZOO, then  O and  P will zoom in and out on the demodulator frequency.

Tip: When you zoom, you are changing the span, but you are not changing the display FFT size, so as you zoom in, less and less detail becomes visible from the FFT process that drives the spectrum and waterfall. To reduce this effect, use a higher density FFT ( Left-clickDSP to alter), such as 16384. This is dense enough that you can zoom in about 16x without going to multiple-pixels per FFT bin, or in other words, without the display looking "blocky." This takes more samples to compute, so it will run slower, but that's the nature of the beast, it's a compromise between the amount of data coming in, and the speed the FFT can be computed. A higher sample rate will speed up FFT generation. A faster computer will not.
Note: If you change your tuning while zoomed in, and then zoom all the way back out, then you will be returned to the tuning in effect when you first began the zoom. This can be a little disorienting if you're not aware of how the zoom operation restores the original center and demod settings when fully zoomed out.

Note that as you adjust the frequency, the information box above the memory selection buttons tells you what portion of the spectrum you are in, as in what ham band, what broadcast band, what CB channel and so on.

You can press < BC, BC >, to move to the next or previous broadcast band, or press the < AR, AR > buttons to move to the next or previous amateur band. When using these, the band edge will be located 10 KHz from the left edge of the display as long as there is room to do so. APH sets the left edge to the amateur phone (voice) regions for these operations, if you're not interested in CW or data transmissions. Holding the tuning buttons down will cause them to repeat.

KLK locks the keyboard to prevent unintended keystrokes from altering system settings.

As mentioned above, there are quite a few keyboard commands that allow you to conveniently adjust frequency without reaching for the mouse. Before using them, however, you should Left-click KLK once if it is illuminated, and twice if not; otherwise, sometimes OS X will "eat" your keystrokes and the program will not recognize that you have pressed a key. See the reference section for a complete list of keystroke commands. You can also press  K to view a dialog containing all of the keystroke commands. You can also Left-clickRef to examine or alter the assignment of any key to any command.



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