[TowerTalk] Shortened Elevated Radials_Choke Balun Needed

[Jim Brown]

On 8/30/2020 9:55 AM, Jeff Blaine wrote:
> You can also make the vert longer than 1/4 WL and that will raise the R 
> but introduce Xl.  Fortunately a series cap fixes the Xl.  I believe 
> that higher natural R **may** offset a bit the effect of the ground loss 
> as the ground loss is a smaller % of the vertical element's R.  Doubt I 
> worded that right - should not have attempted it on so little coffee 
> this early in the AM.

 From the beginning, I've done exactly that with my Tee vertical that 
has on-ground radials of random length. I tuned it to 50 + jX, then 
added C to tune out jX. N6BV modeled the vertical (but not the radials) 
in the licensed version of NEC and found no significant difference in 
radiation efficiency, but the matching method works very well with low 
ESR caps I was able to buy surplus in Si Valley. You know whether they 
are low ESR by transmitting a while and noting whether smoke emerges or 
they are hot to the touch. Virtually all of the HV caps I bought new 
from Newark or Allied emitted smoke.

I also added a second vertical wire in parallel with spacers to increase 
SWR bandwidth, which changed the tuning slightly. That antenna started 
out with about 85 ft vertical; about five years ago, I had climbers 
raise the rigging points to make it 100 ft vertical and tweaked both the 
horizontal portion and the matching C.

73, Jim K9YC