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

[Jim Lux]

On 10/31/20 4:11 PM, jimlux wrote:
> 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

Curse spellcheck - Owens Valley
the Owens Valley Radio Observatory (OVRO) is located near Big Pine 
(between Bishop and Independence)..


> 
> 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.