Practical_Antenna_Handbook_0071639586

614 P a r t V I I : T u n i n g , T r o u b l e s h o o t i n g , a n d D e s i g n A i d
Figure 27.20 MFJ 259 VSWR analyzer.
guably its most useful feature is its sweep display of SWR or R or X versus frequency,
invaluable for quickly determining the effect of an antenna adjustment on its characteristics
over the entire band of interest. In addition to being able to provide values of capacitance,
inductance, line length, and line loss, the VIA includes a serial port for
high-Âresolution data transfer to a PC and/or remote control by a PC. The unit also can
store plots in nonvolatile memory, and it has a Smith chart mode as well. Despite its
considerable capabilities, the VIA is the “low” end of a family of analyzers, the rest of
which are intended (and priced) for commercial applications such as cell phone systems
and land mobile repair shops.
Because these units employ wideband small-Âsignal detectors to keep costs down,
they are susceptible to errors from ambient RF fields within their frequency ranges,
such as might be experienced when using the device in the presence of active transmitters
or in the vicinity of broadcast stations, both AM and FM. Generally, it is not wise to