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In KC908, the analog bandwidth is wider than SPAN, usually around
50MHz. In other words, signals that are not visible on the spectrum can also
cause overload. After overload occurs,the instrument usually will displays a
prompt, but it is not quite reliable.
Increase REF as much as possible to prevent overload, as long as you are
satisfied with sensitivity. In receiver mode preamplifiers should be turned
off.(AMP set to 20dB or 0dB)
After overload, the spectrogram will be distorted and clutter will appear. In
this case, increase REF, lower the gain and increase attenuation(LEV-GAIN-ATT)
until the everyting is back to normal.
The front stage of the instrument may also be overloaded besides the
overload of the ADC. It's also called blocking. Strong signals causing block
may be far from the set frequency, they can still be relevant as long as they
are within the corresponding preselector band(see 2.7). This situation often
occurs when there's a base station or a broadcasting station nearby. It should
be noted that the anti-blocking capability of this instrument is relatively
strong, due to the usage of high compression point amplifiers and mixers. But
the cost is power consumption.
The common phenomenon of pre-stage overload is: the signal peak value
is reduced, the noise floor is raised by 20~30dB, and a lot of burrs appear on
the originally independent signal. User can try changing the antenna
orientation, increase REF, or set manual attenuation (LEV-AMP-ATT). It means
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