9 bandscanner
the bandscanner operates in conjunction with the graphics display.
it is not a wideband fft type routine that displays channels either side of the current frequency, rather it uses the receiver as a scanner. it requires the following facilities of the rig to be available to the controller:
• control of volume either via dsp or i2c digital pot
• control of hang time via i2c dac
• graphics display (320x240)
when selected, the controller mutes the receiver, switches the hang time to 0 and starts to scan the receiver over a range of frequencies centred on the current frequency. the width of the scan is selected according to the current receive filter bandwidth, and is determined by two scan rates that are set using cfset and selcf.
when operating, every 10 msec the rig measures the current receive signal level and steps the frequency on. every 8 measurements it displays the set of measurements on the screen. it scans 200 points, displaying 200 pixel width on the screen which therefore takes 2 seconds per scan. the vertical display has the same linearity and range as the full rig itself, displaying 120 db at a scale of 1db per pixel.
one additional parameter is used by the controller. when the rig switches back to the start frequency, it takes time to lock. the rig could simply wait for the pll to relock, but instead it waits a short delay. this delay is configurable.
if the tuning control is moved whilst scanning, a small cursor just beneath the scan display is moved from left to right. this indicates the frequency that the rig will be tuned to when the scan is cancelled. note that at the moment the range of the scan is not limited to the edges of the band, so it is possible to move the cursor beyond the edge of a band. when the scan is cancelled however, the software will not allow the rig to be tuned outside the band and it will be set to the edge of the band.
