Topband: AIM4170 antenna analyzer

[Jim Brown]

On Tue, 04 Sep 2007 09:17:38 -0500 (CDT), John Kaufmann wrote:

>I compared the AIM4170 to the AEA VIA Bravo, which costs four times
>more, and the AIM is more accurate at very low impedances (< 10 
>ohms) and very high impedances (> 1 kohm).  

I don't own one, but have done "round robin" testing with several 
measurement systems of very high impedance components that have 
pretty low stray capacitance like ferrite chokes. These components 
are difficult to measure accurately, because they are essentially 
parallel resonant circuits with C values on the order of 1-7 pF.  
The stray of the analyzer adds to the impedance of the component 
being measured and shifts the apparent resonant frequency of the 
component. The AIM appears to have several pF of stray C that it is 
not able to "subtract out" of the measurement. This is not an issue 
when measuring antennas, but it's a very big deal if you're 
measuring ferrite chokes.  I own the TenTec VNA (designed by TAPR). 
It has the same limitation. 

73,

Jim Brown K9YC