I would not unwind any turns at this time. Just add wire to the end section. It looks like coil which probably acts like an 80 meter trap, was carefully designed to trap 80 meter radiation from entering the end section of the antenna. IF this was the design intent, if the number of turns on the end coil (trap) is even just changed slightly, this may solve the 160 meter problem, but will change the resonant frequency of the "trap" so it will not isolate the end section on 80 meters and may goof everything up on 80. After you have some experience in a few years you may be able to re-design coils and traps for possibly better performance. The use of a large coil like you have, is an acceptable design 160 meter operators sometimes use instead of a conventional L C trap.
We still do not know your objective on 160 meters. Is it local nets/rag chews, regional possibly including a few states, or "DX" which on 160 meters means anything over perhaps 2000 miles. IF DX is your primary objective, then an inverted L is a very good way to go, in fact most DX on 160 probably is worked with something like an inverted L. Ideally, the inverted L will have a vertical radiator at least say 50 feet, or even longer. Then the remainder of the 140 foot radiator is made up of a wire horizontally from the top of the vertical wire. Often we cannot make the wire horizontal, so need to slope it downward, when you slope it downward the performance will suffer. Some folks build successful inverted L antennas with vertical heights of less than 40 feet. but the L may still be useful so do what you can. The vertical part can be something like a wire (or aluminum tube) suspended away from the tower several feet. This idea may be acceptable for an inverted L, but only if you can bury, or lay on the ground hundreds of feet of wire. Something like at least 8 radials something like 100 feet long, but more shorter radials will work. Ideally the vertical would have symmetric radials, however most of us have radial fields quite compromised, like radials only say over 180 instead of 360 degrees. An inverted L may have some features some folks like. Most of the radiation occurs in the vertical section, and is at relatively low angles which is good for DX. However some useful radiation occurs in the top "horizontal" wire which may be a big help for more regional or local QSO's. I have used inverted L's on 160 for many decades, typically with the vertical only 50 or 60 feet high, with good and compromise radial fields. With 100 watts of CW, or even QRP power levels I have had many QSO's out beyond 1500 miles. In fact, probably 99 % have been over 1500 miles since the Seattle area is the closest place with significant ham populations from my location N E of Anchorage, Alaska.
Get an antenna book, or a copy of 'Low Band DX'ing" if you can find one. Also there are 160 meter forms on the internet, and over the years some articles in QST with antennas for 160. Some folks spend more money and time on their radial field, than on the antenna. I only put in a very compromised radial field on my first inverted L. I did not know if I could or even enjoy 160 meters. This poor radial field gave me an opportunity see if I wanted to spend time and money on 160. This temporary field, which was further degraded by construction back hoe's, gardening, corrosion of some wires, was not improved for another 3 ? decades. I did not have good scientific documentation of the before and after performance, but subjectively it seemed like a significant improvement. I have no idea of how many dB I gained, but I would not be surprised if it was as much as 3 to 6 dB.....this is just a very WILD guess. Presently I have about 32 radials the same length, I believe around 80 or 90 feet. Some curve around the house, a few have 90 degree bends (not good) and portions of the compass are not visited with my wire radials. This is roughly half a mile of wire. A few ground rods will be a poor substitute, but even a dozen 40 foot radials over the 360 degrees would be enough to get you on the air to start. We cannot answer all questions here, so read up on 160 meter antennas.
Rick KLCW
