Antenna Analysers, Network Analysers
Network analysers (aka antenna or SWR analysers) serve to determine measurement parameters about radio components like antennas, cable, filters, amplifiers etc. A distinction is made between scalar and vector network analysers (SNA vs VNA). Scalar analysers usually measure only the amplitude of a value. This is sufficient in many cases, like for measurement of reflection or resonance matches. A vector analyser measures additionally the phase (angle) of a signal. This allows to calculate complex data and display measurement for example in a Smith chart. Other measurements like group delay or phase shifts by filters also require measurement of the phase angle.
A common application of a network analyser with radfio amateurs is the diagnosis of an antenna. It is very easy to measure the resonance frequency or the resonance match of an antenna. An analyser can also be used to measure cables, for example to find hidden faults in connectors, or water in a cable. Adjustment of a filter becomes much easier with a continues display of a network analyser, as wel las the alignment of an amplifier. Last but not least a modern, computer supported network analyser is very helpful in learning how HF circuits work, by monitoring how certain operation affect various parameters.