[TowerTalk] Antenna Analyzers

[Jim Brown]

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