Topband: T-loaded vertical

[Paul Christensen]

>"With respect to current distribution with the lowered resonance -- N6BV
modeled it in his NEC-4 licensed software, and found no increase in the far
field compared to a resonant antenna."

Looks like I accidentally cross-posted to the TowerTalk list, so I'll bring
it back...

Jim,

I didn't see any change either until I ran a "what if" analysis with several
types of compromised radial systems.  The change wasn't too significant, but
4Nec2 with NEC4 did show improvement when running the surface wave model.
With a reasonably good radial system, I didn't find a modeled change in
field strength.    

With our current 80 ft. T, we've not experienced any discernable pattern
distortion to the HF Yagis, including a full-size 4L 40m monobander at 140
ft. but going to a 100 ft length may further reduce any mutual coupling.
With the T resonated at 1400 kHz, that also helps to minimize mutual
coupling to our 200 ft. diameter Hi-Z 8 on 160m.  We've not seen a need to
use a relay to open-circuit the base feed.  The Hi-Z 8 is capable of some
extraordinary F/B but I find big changes throughout the evening.  There are
times when F/B rejection is 30+ dB and other times it may be on the order of
12 dB depending on arrival angles and probably some other factors that are
unknown to me.

Paul, W9AC