If the drive is intact, you might proceed this way on the way to using it
as a 10-15 driver. First, at some standard but accessible height, test
the driver alone (match removed) and record the feedpoint impedance data,
such as Z, resonant frequency on each band, etc. These are reference
Now, try removing the outer ends and the outer traps. Theoretically, the
result is a duo-band driver. However, you may have to change the inner
(10-meter) length and add some to the new out (15 meter) length to restore
the resonant frequencies as in the reference data. (No need to add that
this is a good time to clean everything.)
The old match was likely optimized for 20 meters, so you may wish to
recalculate and adjust the hairpin (if that was used on that model) beta
for 15 and 10 alone.
Likely, once set into the combine beams you are planning, further
adjustments will be needed, but this may get you into the ball park.
Hope these notes are useful. Good luck interlacing that many elements--it
may not be as easy as it seems.
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