On 12/6/2018 2:36 AM, Máximo EA1DDO_HK1H wrote:
Most ham devices cover HF and some of them VHF. Good for a majority of users.
For those with UHF needs... best handheld VNA I know (not professional devices)
is the KC901V or KC901S+.
In this discussion, it is important to understand the difference between
a VNA, which is a two-port device, and a VIA (vector IMPEDANCE
analyzer), which is a one port device. If it's got only one connector on
it, it's a VIA. A VIA measures S11, which can be used to compute the
impedance, and a suitable sweep can be post-processed to do TDR. A VNA
adds the capability to measure S21, the GAIN between its input and
output. Maybe I'm dense, but I can't think of a reason to need a
handheld VNA, or to need one on a tower.
S21 measurements are typically used to measure gain of electronic
systems, the response of bandpass filters, including systems with
cavities, and the isolation between antennas. I also use S21 to measure
high impedances, like common mode chokes and small values of
capacitance. For the latter measurement, a specially constructed test
jig is required.
Most antenna analyzers are single-port devices, and the best of those
are VIAs. This includes all of the Rig Expert units, the SARK, the
FA-VA5, and all of the single-port AIM units.
73, Jim K9YC
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