Elecraft KX3 Owner's Manual - Manual (Page 27)

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including the apparent noise floor of the
receiver, will “roll off” by these amounts.
§ If you have an accurate signal level source
(such as an Elecraft XG-series signal source or
a signal generator), you can calibrate the signal
amplitude following directions provided by the
SDR program.
§ After you are comfortable with setting up and
using the spectrum display, you can connect the
USB/serial cable between the PC and the KX3.
§ Typically, some spectral noise will appear in
the display in the form of “spikes” or
modulation sidebands. These can arise from
several sources, including nearby power
supplies, ground noise, or the computer and its
peripherals. You can often use isolation
transformers, improve grounding, and shielded
cables to reduce the amplitude of these signals.
Note: Try setting up without isolation
transformers, initially. They can sometimes
add signal pickup that makes the spectrum
display much noisier.
§ Some low-level spikes may appear in the
spectral display that originate at the KX3.
These are usually low enough in amplitude to
be masked by band noise when a suitable
antenna is connected.
§ The HDSDR program can also display the
actual frequency range in use if it is set up to
communicate with the KX3. To do this, set up
the program to use KX3, K3, or Kenwood
protocol using the procedure and support files
described on the HDSDR website. Connect the
KX3’s ACC1 jack to a USB or RS232 port on
the computer (see pg. 5). After configuration,
the program should then correctly display the
actual signal frequencies as you tune the KX3.
You may also be able to tune the KX3 from the
program, depending on the program’s features.