开云体育

Software defined receivers are a useful tool. Some of them can see a
wide area of the spectrum at once: about 2 MHz for RTL-type receivers
and nearly 10 MHz for Airspy or SDRplay. The dynamic range of the RTL
receivers is limited and only useful for finding egregious problems,
the higher resolution Airspy and SDRplay are good enough for FCC
compliance testing. You can get software that turns them into a slow
spectrum analyzer by repeatedly retuning the receiver and grabbing
another sample.

SDRs that use a QSD (Softrock, RS-HFIQ, KX2 and KX3, etc) have a much
more limited bandwidth; up to about 150 KHz at a time if you use an
audio card with 192 KHz sampling. They are less useful for broadband
testing, but their excellent low noise performance makes them a great
tool for exploring problems that are near the carrier.

SDRs that use direct sampling (an RF-rate ADC) could in theory do a
spectrum analysis of the entire HF spectrum at once. But it would be a
challenge to build a computer fast enough to do that. And some
incorporate switched analog filters on the input that would make that
less useful.

The spectrum scope features in some of the fancy big name transceivers
can also be useful. The resolution of the display that is built into
the radio is likely to be too low to be useful, but some rigs also let
you connect an external monitor that lets you see more detail about
the signals.