Bandscope; Features Of The Fft Bandscope - Kenwood TS-990S In-Depth Manual

Bandscope

The TS‑990S is the first KENWOOD transceiver to employ a FFT (Fast Fourier Transform) bandscope, which is different
from bandscopes based on a sweep technique widely used in transceivers of other manufacturers.
The FFT bandscope features outstanding "high spectral display refresh speed" and "adjacent signal discriminability
(frequency resolution)". The FFT bandscope is newly developed as a proper method to grasp the frequency band status
which from time to time varies in the environment where variety stations are active on their own style.

Features of the FFT Bandscope

The sweep bandscope refreshes the spectral display, detecting the signal level by literally sweeping the displayed
frequency span from end to end. In contrast, the FFT bandscope analyzes signals of a certain frequency width (10 kHz)
all at once. If there is a wide displayed frequency span, frequency analysis by FFT is repeated to refresh the spectral
display after merging the cumulated analysis results.
SWEEP TYPE BANDSCOPE
Gradually analyze the edge of the displayed frequency
span and fresh the display.
Fig. 78 Differences in Spectral Analysis between Sweep‑type and FFT‑type Bandscopes
If the spectral display refresh speed is increased in the sweep‑type bandscope, the frequency resolution may deteriorate
and the spectral display may distort; hence, the spectral display refresh speed has a limit (approximately 5 times per
second). On the other hand, the FFT‑type bandscope is still capable of high frequency resolution even if the refresh
speed is doubled compared with that of the sweep‑type bandscope.
The high frequency resolution facilitates you to distinguish multiple adjacent CW signals. Narrowing the displayed
frequency span enables you to distinguish closer adjacent signals. For example, if there is a 5 kHz frequency display
span, a CW signal distant by 40 Hz can be distinguished.
Fig. 79 Reception of two signals with a frequency difference by 40 Hz
FFT TYPE BANDSCOE
Analyze the certain bandwidth (10 kHz) at once and
refresh the display.
DSP 06
51