[TowerTalk] Cover antennas - the good news and the bad news

[jimlux]

On 10/31/20 2:19 PM, Michael Tope wrote:
> It would interesting to take a known good antenna like a monoband Yagi 
> (or perhaps a SteppIR) and do a set of measurements over the course of 
> several days to evaluate the measurement repeatability. If someone had 
> designs on doing a K7LXC/N0AX type antenna evaluation study, this would 
> help determine the size of the error bars for measurements of different 
> antennas taken over the course of several days. Stable weather would 
> likely be a desirable characteristic of the measurement environment (no 
> drastic changes in ground characteristics during the measurement period).

excellent point..


> 
> I had to use Google to get the bagpipe joke :-)
> 


Here's some actual measured data from a site in the Owen's Valley

http://jim-lux.blogspot.com/2020/10/permittivity-under-antennas-there-is.html

There were significant variations in the surface soil properties (4" 
deep), but since skin depth for HF is substantially more, it's probably 
stable over a day or two, assuming it doesn't rain or it's continuously 
raining.

But substantial changes over months, so if you've got a vertical, that's 
going to make a difference.