Elecraft PX3 Owner's Manual - Manual (Page 32)

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PX3 Compared to the P3 and PC-Based Panadapters
The PX3 can display spans of up to 200 kHz, whereas most PC-based panadapters using I/Q demodulation are
limited to about 40 kHz spans. The PX3 is also very tightly integrated with the KX3, making it very convenient
to use.
Like PC-based panadapter applications, the PX3 makes use of baseband RX I/Q signals from the KX3. These
signals are sampled by an analog-to-digital converter (ADC), and then mathematically processed to create the
spectral and waterfall displays.
Because the process is analog, it is subject to possible noise pickup from various sources, including switching
power supplies, 60-Hz AC, ground loops, and interface cables. That is why we recommend you use the cables
supplied (see PX3CBL on page 5) and arrange the PX3 and KX3 as described under Setup and Connections on
page 6.
In the case of a PC panadapter application, a sound card must be used and performance will only be as good as
the ADC used on the sound card. The PX3’s ADC is very high performance, resulting in a low noise floor, and
the supplied cables are very short to minimize noise pickup. However, the PX3 is still subject to pickup from
some noise sources, and the operator may see a few discrete spurs from station power supplies, etc., especially
when wider spans are used (over 70 kHz or so). I/Q demodulation may also show a greater number of artifacts,
such as opposite-sideband images, than I.F.-derived digital down-conversion (which is used in the P3).
However, when the PX3 is properly aligned, such artifacts will be significantly suppressed (typically by 60 dB
or better).