On Wed, Feb 24, 2021 at 03:28 AM, Barry Feierman wrote:
Nano VNA: An Antenna Stethoscope
I will add my appreciation to Roy's and to his comment about the slightly erroneous TDR explanation.
There are a couple of items i would take up with you-
The picture /display of attenuation versus frequency of the RG-8 is enlightening and you could add a comment that the regularity and smoothness of this graph is a direct indication of the qualities of the cable being sampled. The 'smoother' the better! There are some very nasty variants of Super-8, RG-8, or RG-8Mini type cables with markedly worse characteristics marketed around the world.
I would choose another way of talking about dipole antennas than showing them without a balancing transformer (1:1 balun) at the centre feed point.
As without a balun here one will always have a third element to the antenna i.e. the outside of the coax feeder cable and this extra element will modify all the impedances measured.
As an antenna it still works with both horisontal and vertical radiation components but as a demonstration - I have serious doubts about the results.
Peter
