Topband: Looking to improve TX antenna Efficiency

[Steven Raas]

Last 'Season' was my 1st real dive into 160m. Running a 'InvL' ( which
I will describe lower in detail ) and 100w, I managed to pull 19 DXCC
and 48 states cfmd. I am in looking into ways to improve my TX antenna
efficiency, for this season w/o getting to crazy . (rx antennas are in
the works and a different topic )

Current TX antenna is as follows: (Tuned in shack / not self reasonant )

Main Element: 32 feet vertical - 90 deg bend ( the 'L' ) which runs
43' horzontally pointing north. Then, another 90 deg bend, and
ascending 26' in length ( from 30' up to about 11' above ground
running from west to east. ), then..you guessed it.. another 90 deg
bend that now runs to the south flat top for 27' ( @ 11' up )

Ground radials qty 24. Min length 22' - max length 62' ( from az 330
deg - 70 deg with the longer radials pointed from 35-60 deg az)

The FCP idea is not practicle for me @ this point in time.

My Thought.. add a Coil @ the 30' point of the main vertical run made
from perhaps 1/8th inch copper tubing ( refrigerant line ) in a fairly
large diamater ( 16-20" ), perhaps 14-20 turns even spaced, using
perhaps drilled lexan as spacers.. Try extending the vertical run
another 8-10' or so.. and then the rest of the antenna as is. Going
above 40' vertical is not an option @ this point in time either. ( yes
i know the more vertical the better its just a no-can-do for now)

At the moment the antenna's best 'swr' is at roughtly 1818 khz @ 2:1
there is no resonant point that I can find within the 160m band. ( no
antenna anyalizer either - Mabey santa will provide ) My best guess is
that in its current configuration... the antenna is probabally in the
8-12 ohm area.. I have nothing solid to back that up however.

At the feed point I have a coaxial choke, 21 turns on a 8" form, the
cable is similar to RG213 , with the exception the center conductor is
solid. ( its actually 50 ohm quad shielded cable i got form a place I
used to work, HP node cluster inter connect cable. .405" & blue in
color,  i cant remember the vf on it but i did spec it out a while
back, and its ok for HF use. )

Or, tuning the antenna @ the base with a variable cap. of  sufficent
size, or perhaps even both?

I know there is NO magic that can come..im just trying to improve on
what I have and can do @ this point in time.

Suggestions, thoughts,  flames and raised brows are all welcome.

Steve Raas
N2JDQ