[TowerTalk] Ground Screen and a Loop

[wb0m at flashdog.us]

On Jun 17, 2009, at 6:44 AM, "Jim, K9YC", wrote:

> I didn't mean to be a PITA, but I was running for the airport when I  
> typed
> that reply and wanted to give you a fast response that was right..."

The short, the "RTFM" answer struck me the wrong way since I was  
trying to learn from others. Especially after a long day. I apologize  
for my snippy reply. And, BTW, thanks for taking the time to reply.

As I interpret the conventional wisdom of ground effect on antennas,  
according to the ARRL antenna book and ON4UN's "Low Band DXing",  the  
theory is that an antenna low enough to the ground will result in  
ground losses except under perfect ground, which can be man-made  
(counterpoise) or natural (if you're lucky enough). In my mind, adding  
a ground screen under that corner should reduces ground loses. Of  
course, how much in negligible. In L.B. Cebik's paper on NVIS loops  
with ground screen there is a bit more gain with a ground screen. But  
the size of the ground screen, 1 wavelength x 1 wavelength is really  
big for my space - actually impossible.
Also, on a related note, since I'm using a antenna coupler (Icom AH-4)  
and 210' of wire, as the antenna is "tuned" (for lack of a better  
phrase), does the wavelength of counterpoise change also? Since the  
coupler matches the impedance for the antenna, do the parameters on  
the counterpoise change, also? This is straying from the loop  
configuration, but is more of a question using a vertical and  
counterpoise situation. My thought process is to build a counterpoise  
under the vertical to match the wavelength of the wire (whatever  
length) for the best results.

Any thoughts anyone?

73,
Jeff