to the first is to be taken is determined by dividing by ten the frequency of the voltage controlled oscillator at which the previous sample was taken and subtracting the answer from the previous frequency then the computer turns off the power to the instrument and awaits a command to measure the next spectrum step s10 each spectrum measurement takes 30 frequency samples across a range of 40 hz to 1000 hz for example each frequency 34 bin 34 is aligned with the adjacent frequency 34 bin 34 so that their passbands intersect at their 3db rolloff points the filter 34 q 34 which is set by the resistors r1 and r2 in fig2 is constant across the frequency spectrum so that the bandwidth is narrower at the lower frequencies q f bw see fig4 and 5 the filter 34 q 34 may be set to about 9 thus at the high frequency end of the spectrum the bandwidth 1000 9 is about 111 hz at the 3db points and at the low frequency end of the spectrum the bandwidth 40 9 is about 4 hz this permits a faster sweep at the high frequencies because of the increased bandwidth the frequency sweep ramp from the ramp generator being an rc discharge is non linear the sweep is conducted as rapidly as possible with acceptable frequency spectrum information the data stored in the computer may be offloaded and processed in an outside.