Topband: QEX article and T-vertical improvement

[Steve Flood]

I currently have a wire T-vertical with a 75-ft. vertical portion and a 75-ft. topload wire over about 60 radials.
Feedpoint is around 25 + j0 at 1.825 Mhz, which I match with a toroid 1:2 unun.

The latest issue of QEX has an article about maximizing radiation resistance by putting the current maxima halfway up the vertical.
EZNEC shows me that by extending my T topload wire to 140-ft. long, the current maxima will move up to the middle of the vertical, and my feedpoint will be around 37 + j238 at 1.825 Mhz.   I would replace the unun with a switched or adjustable L-network for matching across the whole band, and perhaps other L-networks for 80 or 40.

A couple questions for the group....

1.  Supposedly I will end up with higher radiation resistance and efficiency, and I assume higher effective radiated power.  But what am I giving up?
2.  Should L-networks be located in  an RF screened enclosure?  I have a large plastic NEMA enclosure I can house the whole matching show in, but should I line the interioir with screening of some sort?

Thanks,

Steve
KK7UV