[600MRG] XSH/20 SWR fun

[Rudy Severns]

As some of you may have noticed, I've been QRT the last couple of nights. 
I'm having an interesting time with my SWR.  As usual we had a long dry 
summer.  While digging the holes for the guy anchors for my new 160m 
vertical I found my soil bone dry and hard as a rock at least two feet down. 
Digging required a large crowbar to break up the soil.  My 630m antenna was 
adjusted in mid summer, SWR=1.1 @ 476 kHz the minimum SWR frequency.

Two days ago the drought broke and we got two inches of rain over 24 hours. 
The morning after the rain I noticed my transmit power was down.  A quick 
check showed my SWR @ 476 kHz was 1.9 and the minimum SWR point had moved 
down to 469 kHz.  During the day as the sun dried out the ground the SWR 
minimum moved steady upward but then we had more rain and it shifted down 
again!

Rather than run back and forth retuning I'm just going to wait a few days 
until things stabilize.  Last winter the SWR was very stable once the soil 
got soaked.  I was a bit surprised my tuning was so sensitive to soil 
moisture.  I have 128 150' radials which extend beyond the top-hat.  I 
thought that would immunize me but not so.  This may explain in part why the 
pro's often use several hundred radials under short top-loaded verticals. 
These radials systems typically have a radius somewhat greater than the 
top-loading radius.

Will be back on shortly.  73, Rudy